Thanks everyone for all the feedback received on the last thread I posted and I hope it was at the least an "eye-opener" for some.

 

I thought it would be a good idea to keep details of any advice given and a list of recommendations somewhere on this page (hopefully an admin will make it a sticky at some point so that it is easily found).

 

Looking at my comments so far, these are the ones that I feel belong in here, if you have any others then please contribute or ask futher questions which hopefully will make this an interesting FAQ thread one day.

 

Quotes so far:

 

Oilman c/o John Rowland (Silkolene/Fuchs R&D Chemist)

 

So, the chemistry of “synthetics” is complex and so is the politics!

 

The economics are very simple. If you like the look of a smart well-marketed can with “synthetic” printed on it, fair enough, it will not cost you a lot; and now you know why this is the case. But, if you drive a high performance car, and you intend to keep it for several years, and maybe do the odd “track day”, then you need a genuine Ester/PAO (Poly Alpha Olefin) synthetic oil, such as PRO S or PRO R. This oil costs more money to buy, because it costs us a lot of money to make, very simply, you always get what you pay for!

 

 

Oilman

 

My opinions are frank but based on facts so I'll apolgise in advance if I upset anyone but I will ALWAYS give you the "best advice", you don't have to take it.

 

Finally, oil for the 300zx is an interesting one as the recommendations I have had are based around the Manufacturers which is 10w-40 Semi-syn however, depending on driving conditions, the following grades can be considered 10w-40 semi-syn,10w-50 Fully-syn, 5w-40 fully syn and 15w-50 fully syn.

 

These all have different advantages to the performance of the car depending on how you use the car. Short journeys, long journeys, track days etc....

 

 

deve8uk

 

So how about sugesting something for a zx with minor mods, running approx 10psi boost that is a daily driver and normaly does short trips and only rarely gets booted. And I do mean rarely here.

 

 

Oilman

 

Firstly bear in mind that the car was designed to run on 10w-40 which is the manufacturers recommended oil but as just about all 10w-40's that I know of except for one are semi-synthetics I would go for fully synthetic as it has a higher resistance to thinning down with temperature (a good one that is, not just an excuse for a synthetic with a pretty label) as they stay in grade longer.

 

 

Oilman

 

For short journeys and lots of cold starts, you need an oil that circulates quickly as this is where 70+ percent of the engine wear occurs so rather than using a 10w consider a 5w, its thinner and circulates more easily. 0w is even quicker but may be too thin and you could end up with oil seal leaks.

 

For faster longer journeys where the engine is operating a high temperatures (hard driving) I would consider a 10w-50 or 10w-60 to give more protection at the top end but you want an oil that has a high resistance to thinning down and "stays in grade" longer. Ester is the best for this (see note below).

 

For racing and track days, you need an oil that will give more protection still and I would consider a 15w-50 which is a recognised motorsport and racing oil which will protect you almost entirely at the top end.

 

 

RichardSmith

 

What are your views on Millers XFS 5w40 and Shell Helix Ultra 5w40 fully synthetics?

 

 

Oilman

 

Difficult to comment really as I've never stocked Shell or Millers. I would be happy using Shell but based on Millers prices, I wonder about the quality, the first post here may be relevant to their oils but without the data it's difficult to say for sure.

I'll try to speak to some technical bods on monday and see if they have any data or experience of these oils.

 

Here are some comments so far for kick off.

 

Cheers

Simon

Yes but follow the following procedure:

 

Flushing Proceedure (Don’t use flushing oils or additives)

 

1. Warm up engine to get oil circulating

2. Turn off engine and drain old oil

3. Fill with new oil to minimum (you will be wasting this)

4. Warm up engine to get oil circulating

5. Turn off engine, drain new oil and change filter

6. Fill to marker on dipstick

 

Cheers

Simon

Yes but follow the following procedure:

 

Flushing Proceedure (Don’t use flushing oils or additives)........

 

Cheers

Simon

 

Why's that, Simon?

 

Richard

Because they are made up of components that do more harm than good.

 

A good quality oil contains detergents that continuously flush the oilways and you should not need to use further detergents.

 

Cheers

Simon

Continuing on, part 2 of the lesson.

 

Building a good oil.

 

It is impossible to make a good 5w-40 or even 10w-40, using only mineral oil. The base oil is so thin, it just evaporates away at the high temperatures found in a powerful engine that is being used seriously. Although there are chemical compounds in there to prevent oil breakdown by oxygen in the atmosphere (oxidation) they cannot adequately protect vulnerable mineral oil at the 130 degC plus sump temperatures found in a hard working turbocharged or re-mapped engine.

 

The answer to this is synthetics. They are built up from simple chemical units, brick by brick so as to speak; to make an architect designed oil with properties to suit the demands of a modern engine.

 

The synthetic myth

 

The word “synthetic” once meant the brick by brick chemical building of a designer oil but the waters were muddied by a court case that took place in the USA some years ago. The outcome was that the right to call heavily modified mineral oil “synthetic” was won. This was the marketing executives dream; the chance to use the word “synthetic” on a can of oil without spending much extra on the contents!

 

Most lower-cost “synthetic” or “semi-synthetic” oils use these “hydrocracked” mineral oils. They do have some advantages, particularly in commercial diesel lubricants but their value in performance engines is marginal.

 

TRUE synthetics are expensive and in basic terms there are three broad catagories, each containing many types and viscocity grades:-

 

PIB’s (Polyisobutanes)

 

These are occasionally used as thickeners in motor oils and gear oils, but their main application is to suppress smoke in two-strokes.

 

The TWO important ones are:

 

ESTERS

 

All jet engines are lubricated with synthetic “esters” and have been for more than 50 years but these expensive fluids only started to appear in petrol engine oils around 20 years ago.

Thanks to their aviation origins, the types suitable for lubricants work well from

-50 degC to 200 degC, and they have an added benefit. Due to their structure, “ester” molecules are “polar”; they stick to metal surfaces using electrostatic forces. This means that a protective layer is there at all times, even during that crucial start-up period. This helps to protect cams, gears, piston rings and valve train components, where lubrication is “boundary” rather than “hydrodynamic”, i.e. a very thin non pressure-fed film has to hold the surfaces apart.

Even crank bearings benefit at starts, stops, or when extreme shock loads upset the “hydrodynamic” film.

 

Synthetic Hydrocarbons or PAO’s (Poly Alpha Olefins)

 

These are, in effect, very precisely made equivalents to the most desirable mineral oil molecules. As with “esters” they work very well at low temperatures and equally well at high temperatures, if protected by anti-oxidants. The difference is, they are inert and not polar. In fact, on their own they are hopeless “boundary” lubricants, with less load carrying ability than a mineral oil. They depend entirely on the correct chemical enhancements.

 

It is a fact that “PAO’s” work best in combination with “esters”. The “esters” assist load carrying, reduce friction and cut down seal drag and wear, whilst the “PAO’s” act as solvents for the multigrade polymers and a large assortment of special compounds that act as dispersants, detergents, anti-wear and anti-oxidant agents, and foam suppressants.

Both are very good at resisting high-temperature evaporation, and the “esters” in particular will never carbonise in turbo bearings even when provoked by anti-lag systems.

 

So, in conclusion, Ester gives the best protection and Ester/PAO combinations have great benefits because they work well together. They are more expensive but worth it if you wish to do the best for your engine.

 

Cheers

Simon

As a user of Castrol RS10-60, please will you email me the report please.

 

simon.axtell@ntlworld.com

 

Simon.

Thanks Simon,

 

Simon :D :D :D

This is probably the longest post on this Forum but certainly one of the most interesting and relevant to all Subaru or High Powered Car Owners.

 

It is the "FULL" unedited transcript of the article written by John Rowland (Chief R&D Chemist for Silkolene) with 40 years experience.

 

It is great educational reading as it is written by a Chemist, not a Salesman so totally based in facts - If you do one thing, read this, it's worth it!

 

I do not work for Silkolene, I'm a car enthusiast who owns an Oil Company that sells their products amongst others. I have Johns express permission to post this article to clear up as he says "the mis-information" on the internet.

 

Lubricating the Subaru.

 

Basically

 

Basically, to use that irritating in-word, engine lubrication is simple, and consequently boring. So I intend to treat the subject “complicatedly”, which may not be an in-word, but makes life far more interesting!

 

So, to take a quick look at the simple picture; the oil keeps moving parts apart, reducing friction and carrying away heat. Where there is metal-to-metal contact there are chemicals in the oil to reduce damage. Because the internal combustion process is always less than perfect, some soot is produced and this must be washed off the pistons and rings by the oil, so it has a cleaning or detergent function as well.

 

The trouble is, all this is just as true for Henry Ford’s original Model T engine as it is for the Subaru or any other high output motor. So where is the difference? The Model T, with 10bhp/litre at 2,000rpm and a single underhead camshaft, was filled with a thick, greenish liquid from somewhere near the bottom of the distillation colums on the Pennsylvania oilfields. It did a vague tour of the internals by guesswork (there was no oil pump) at a temperature around 50 degC, and lasted for 1,000 miles. On the plus side, some of the impurities acted as anti-wear and detergent chemicals. They didn’t work very well, but it was better than nothing. The engine wore out in around 20,000 miles, but even ordinary people, not just amateur rally drivers, were happy to put up with this.

 

The difference begins with the first turn of the key. The modern high-pressure pump would cavitate on the old heavy monogrades, starving the bearings for a vital couple of seconds, even in warm weather. Likewise, cam lobes would suffer as the sluggish oil found its way along narrow oil ways to the valve gear. The turbo bearing (if fitted as the handbooks say) already spinning fast, would also starve, and when it got going, how long would it be before the heat soak-back fried the primitive oil into a lump of carbon? (This was the problem with “modern” oils only 15 years ago).

 

So, a good oil must be quite low in viscosity even in the cold, so that it gets around the engine in a fraction of a second on start-up. On the other hand, it must protect engine components (piston rings for example) at temperatures up to 300 degC without evaporating or carbonising, and maintain oil pressure.

 

Unmodified thin oils simply can’t manage this balancing act. The answer is to use a mixture of thin oil and temperature-sensitive polymer, so as the thin oil gets even thinner with increasing temperatures as the engine warms up, the polymer expands and fights back, keeping the viscosity at a reasonable level to hold oil pressure and film thickness on the bearings. This is called a multigrade.

 

But, this is all too basic! What I have just written was and is relevant to a 1958 Morris Minor.

 

The questions that Subaru owners need to ask are: “Will this thin oil evaporate and be drawn into the intake manifold (via the closed circuit crankcase ventilation), leading to combustion chamber deposits and de-activated catalysts?” and “Will the polymer shear down at high engine revolutions and high temperatures, causing low oil pressure and component wear?” and “Will it carbonise on the turbo bearing?” These are 21st century questions which cannot be answered by a basic 1990’s approach.

 

BUT! Before we head into more complications, some figures………

 

The SAE Business (American Society of Automotive Engineers)

 

Viscosity is the force required to shear the oil at a certain speed and temperature. Oils work because they have viscosity; the drag of a rotating part pulls oil from a low-pressure area into a high pressure area and “floats” the surfaces apart. This is called “hydrodynamic lubrication”, and crank bearings depend on it. In fact a plain bearing running properly shows literally no metal-to-metal contact. Experimental set-ups have shown that electrical current will not flow from a crank main bearing to the shells. Also, the energy loss due to friction (the co-efficient of friction) is incredibly low, around 0.001. So for every kilogram pulling one way, friction fights back with one gram. This is very much better than any “dry” situation. For example, the much over-rated plastic PTFE has a co-efficient of friction on steel of 0.1, 100 times worse than oil.

 

Oil viscosities are accurately measured in units called “Centistokes” at exactly 100 degC. These fall into five high temperature SAE catagories:-

 

SAE No. 20 30 40 50 60

Viscosity Range 5.6 -

 

A decent quality oil usually has a viscosity that falls in the middle of the spec, so a SAE 40 will be about 14 Centistoke units, but SAE ratings are quite wide, so it’s possible for one 40 oil to be noticeably thicker or thinner than another.

 

When the polymer modified multigrades appeared, a low temperature range of tests were brought in, called “W” for winter (it doesn’t mean weight). These simulate cold starta at different non-ferrous monkey endangering temperatures from –15 degC for the 20w test to a desperate –35 degC for 0w. So, for example, an SAE 5w-40 oil is one that has a viscosity of less than 6600 units at –30 degC, and a viscosity of about 14 units at 100 degC.

 

Now, those of you who have been paying attention will say “Just a minute! I thought you said these multigrade polymers stopped the oil thinning down, but 6600 to 14 looks like a lot of thinning to me!”. Good point, but the oil does flow enough to allow a marginal start at –30 degC, and 14 is plenty of viscosity when the engine is running normally. (A lot more could damage the engine. Nobody uses the 24 viscosity SAE 60 oils any more.) The vital point is, a monograde 40 would be just like candle wax at –30 degC, and not much better at –10 degC. It would even give the starter motor a fairly difficult time at 0 degC. (At 0 degC, a 5w-40 has a viscosity of 800 but the monograde 40 is up at 3200!)

 

Another basic point about wide ranging multigrades such as 5w-40 or 0w-40 is that they save fuel at cruising speeds, and release more power at full throttle. But complications arise……..

 

Building a good oil

 

A cave may not be the best place to live, but it’s ready-made and cheap. This is the estate agent’s equivalent of an old style monograde oil. Or you could get Hengist Pod to fit a window and a door; this is moving up to a cheap and cheerful mineral 20w-50. But an architect-designed “machine for living in”, built up brick by brick, is an allegory of a high performance synthetic oil.

 

It is impossible to make a good 5w-40, or even 10w-40, using only mineral oil. The base oil is so thin, it just evaporates away at the high temperatures found in a powerful engine that is being used seriously. Although there are chemical compounds in there to prevent oil breakdown by oxygen in the atmosphere (oxidation) they cannot adequately protect vulnerable mineral oil at the 130 degC plus sump temperatures found in hard worked turbocharged or re-mapped engines.

 

Synthetics are the answer. They are built up from simple chemical units, brick by brick so as to speak; to make an architect-designed oil with properties to suit the modern engine.

 

But sometimes, if you look behind the façade, there is a nurky old cave at the back! This is because the marketing men have been meddling!

 

The Synthetic Myth

 

What do we mean by the word “synthetic”? Once, it meant the “brick by brick” chemical building of a designer oil, but the waters have been muddied by a court case that took place in the USA a few years ago, where the right to call heavily-modified mineral oil “synthetic”, was won. This was the answer to the ad-man’s dream; the chance to use that sexy word “synthetic” on the can….without spending much extra on the contents! Most lower cost “synthetic” or “semi-synthetic” oils use these hydrocracked mineral oils. They do have some advantages, particularly in commercial diesel lubricants, but their value in performance engines is marginal.

 

TRUE synthetics are expensive (about 6 times more than top quality mineral oils). Looked at non-basically there are three broad catagories, each containing dozens of types and viscosity grades:-

 

PIB’s (Polyisobutanes)

 

These are occasionally used as thickeners in motor oils and gear oils, but their main application is to suppress smoke in 2-strokes.

 

The two important ones are:

 

Esters

 

All jet engines are lubricated with synthetic esters, and have been for 50 years, but these expensive fluids only started to appear in petrol engine oils about 20 years ago. Thanks to their aviation origins, the types suitable for lubricants (esters also appear in perfumes; they are different!) work well from –50 degC to 200 degC, and they have a useful extra trick.

 

Due to their structure, ester molecules are “polar”; they stick to metal surfaces using electrostatic forces. This means that a protective layer is there at all times, even during that crucial start-up period. This helps to protect cams, gears, piston rings and valve train components, where lubrication is “boundary” rather than “hydrodynamic”, i.e. a very thin non-pressure fed film has to hold the surface apart. Even crank bearings benefit at starts, stops or when extreme shock loads upset the “hydrodynamic” film. (Are you listening, all you rally drivers and off road fanatics?)

 

Synthetic Hydrocarbons or POA’s (Poly Alpha Olefins)

 

These are, in effect, very precisely made equivalents to the most desirable mineral oil molecules. As with esters, they work very well at low temperatures, and equally well when the heat is on, if protected by anti-oxidants. The difference is, they are inert, and not polar. In fact, on their own they are hopeless “boundary” lubricants, with LESS load carrying ability than a mineral oil. They depend entirely on the correct chemical enhancements.

 

PAO’s work best in combination with esters. The esters assist load carrying, reduce friction, and cut down seal drag and wear, whilst the PAO’s act as solvents for the multigrade polymers and a large assortment of special compounds that act as dispersants, detergents, anti-wear and oxidant agents, and foam suppressants. Both are very good at resisting high-temperature evaporation, and the esters in particular will never carbonise in turbo bearings even when provoked by anti-lag systems.

 

Must Have MORE Power!

 

Motorcars are bought for all sorts of reasons, but enthusiasts like lots of power. To get more power, a lot of fuel must be burnt, and more than half of it, sadly, gets thrown away as waste heat. For every litre of fuel burnt, 60% of the energy goes as waste heat into the exhaust and cooling system. A turbocharger can extract a few percent as useful energy and convert it into pressure on the intake side, but only 40-45% is left, and only 25% actually shows up as BHP at the flywheel. 6% goes in pumping air into the engine, 6% as oil drag losses and 2-3% as engine friction. The oil deals with 97% of the friction; so reducing the remaining few percent is not easy. If you doubt that even ordinary oil has a massive effect, take a clean, dry 200 bhp engine, connect it to a dyno and start it up. It will only make 1 bhp for a few seconds. Now that’s real friction for you!

 

Oddly enough, people get starry-eyed about reducing friction, especially those half-wits who peddle silly “magic additives”, which have not the smallest effect on friction but rapidly corrode bearings and wallet contents. In fact, even a virtually impossible 50% reduction in the remaining engine friction would be no big deal, perhaps one or two bhp or a couple of extra miles per gallon.

 

Even More Power!

 

The place to look for extra power is in that 6% lost as oil drag. In a well-designed modern motor, the oil doesn’t have to cover up for wide clearances, poor oil pump capacity or flexy crankshafts, so it can be quite thin. How thin? Well take a look at these dyno results.

 

A while ago now, we ran three Silkolene performance oils in a Honda Blackbird motorcycle. this fearsome device is fitted with a light, compact, naturally aspirated 1100cc engine which turns out 120+ bhp at the back wheel. The normal fill for this one-year-old engine was 15w-50, so the first reading was taken using a fresh sump-fill of this grade. (The dyno was set up for EEC horsepower, i.e. Pessimistic)

 

15w-50

 

Max Power 127.9 bhp @ 9750 rpm

Torque 75.8 ft-lbs @ 7300 rpm

 

After a flush-out and fill up with 5w-40 the readings were;

 

5w-40

 

Max Power 131.6 bhp @ 9750 rpm

Torque 77.7 ft-lbs @ 7400 rpm

 

Then we tried an experimental grade, 0w-20 yes, 0w-20! This wasn’t as risky as you may think, because this grade had already done a season’s racing with the Kawasaki World Superbike Team, giving them some useful extra power with no reliability problems. (But it must be said, they were only interested in 200 frantic miles before the engines went back to Japan)

 

0w-20

 

Max Power 134.4 bhp @ 9750 rpm

Torque 78.9 ft-lbs @ 7400 rpm

 

In other words, 3.7 bhp / 2.9% increase from 15w-50 to 5w-40, a 2.8 bhp / 2.1% increase from 5w-40 to 0w-20 or a 6.5 bhp / 5% overall. Not bad, just for changing the oil! More to the point, a keen bike owner would have paid at least £1000 to see less improvement than this using the conventional approach of exhaust/intake mods, ignition re-mapping etc.

 

Am I recommending that you use 0w-20 in your Subaru’s? Well, perhaps not! The 5w-40, which is a “proper” PAO/Ester shear-stable synthetic, will look after a powerful engine better than a heavier viscosity “cave at the back” conventional oil, and provide a useful extra few BHP.

 

The End

 

However, as with all good things in life, we don’t live in a world of perfect motor cars and therefore we have to look at the lubrication trade-off between longevity, reliability, power and cost, relative to the vehicle in which the oil is being used (a scruffy old XR2i with 192,000 miles on the clockis a very different proposition to your spanking new Impreza). Which is why Subaru (and probably your local dealer) recommends a 10w-50 (Such as PRO S); you could look at a 5w-40 for competition and track-day use, but only the most committed competitor would want, or need, the 0w-20 for the extra 5% power.

 

Cheers

Simon

Oilman, could you please send me a copy of your findings on Castrol RS as I have always used this in my Z. E-mail is arundalep"at symbol"hotmail"dot"com (sorry to be a pain but I get 1200 junk e-mails a week on my old pop account.

 

Thanks,

Sparkz

Oilman how do you rate Mobil 1 ???

Oilman how do you rate Mobil 1 ???

 

Mobil 1 is a very good PAO oil. We stock it and its very popular. However you can go one better with an ester based oil.

 

Contact me for further information: sales@opieoils.co.uk

 

Tech specs http://www.opieoils.co.uk/lubricants.htm

 

Cheers

 

Guy.

Cheers buddy.

i take it its nae gid tae shuv 0-40 in the 32tt

i take it its nae gid tae shuv 0-40 in the 32tt

 

HMMMMMmmmmmmm not sure I would recomend that!!!

 

5w-40 or 10w-50 would be more like it.

 

cheers

 

Guy. :)

cheers oilman , glad i never shuved it init noo 5-40 it will be

cheers oilman , glad i never shuved it init noo 5-40 it will be

 

Good man! you know you can e-mail me for price list at sales@opieoils.co.uk

 

Cheers

 

Guy.

Thought these two articles would be of interest to you all:

 

Surely the thicker the oil the better!

 

This isn't always true - even when using a petroleum oil. Although it is true that

heavier viscosity oils (which are generally thought of as being thicker) will hold up better under heavy loads and high temperatures, this doesn't necessarily make them a better choice for all applications.

On many newer vehicles only 0w-40, 5w40 or 10w40 engine oils are recommended by the manufacturer. If you choose to use a higher viscosity oil than what is recommended, at the very least you are likely to reduce performance of the engine. Fuel economy will likely go down and engine performance will drop.

In the winter months it is highly recommended that you not use a heavier grade oil than what is recommended by the manufacturer. In cold start conditions you could very well be causing more engine wear than when using a lighter viscosity oil. In the summer months, going to a heavier grade is less of an issue, but there are still some things to be aware of.

 

Moving one grade up from the recommended viscosity is not likely to cause any problems (say from a 10w40 to a 10w50 oil). The differences in pumping and flow resitance will be slight. Although, efficiency of the engine will decrease, the oil will likely still flow adequately through the engine to maintain proper protection. However, it will not likely protect any better than the lighter weight oil recommended by the manufacturer.

Moving two grades up from the recommended viscosity (say 10w40 to 10w-60) is a little more extreme and could cause long term engine damage if not short term. Although the oil will still probably flow ok through the engine, it is a heavier visocosity oil. As such it will be more difficult to pump the oil through the engine. More friction will be present than with a lighter viscosity oil. More friction will be present than with a lighter viscosity oil. More friction means more heat. In other words, by going to a thicker oil in the summer months, you may actually be causing more heat build-up within the engine. You'll still be providing adequate protection from metal to metal contact in the engine by going with a high viscosity, but the higher viscosity will raise engine temperatures.

In the short run, this is no big deal. However, over the long term, when engine components are run at higher temperatures, they WILL wear out more quickly. As such, if you intend on keeping the vehicle for awhile, keep this in mind if you're considering using a heavier weight oil than the manufacturer recommends.

The best advice is to is to stay away from viscosity grades that are not mentioned in your owner's manual.

 

Cheers

Simon

THE IMPORTANCE OF THE ADDITIVE PACKAGE

 

Although the basestock of an oil will be a major determining factor in the lubrication quality of an oil, chemical additives play a major part in making sure that it does all that it is supposed to do. The chemical additive package of an oil is just as important to insuring the quality of a lubricant as is the particular basestock used.

The chemical additive package of an oil is designed to perform a number of tasks and each task is performed by a particular type of chemical. The quality of the chemicals used and the manner in which they are blended plays a large part in determining how well the additive package does its job.

 

As the quality of the additive chemicals increases, so does the price. In addition, proper blending takes a great deal of research. This requires much time and, again, money. Therefore, manufacturers will, of course, charge more for motor oils which contain a high quality additive package than those with lower quality additive packages. They simply can't afford not to.

 

Each chemical within an oils additive package plays a different role in boosting the beneficial properties of it's host lubricant (basestock).

 

The additive package must perform the following roles:

 

IMPROVE VISCOSITY CHARACTERISTICS

 

Basestock lubricants have a certain temperature range over which they will flow adequately. The wider this temperature range the better. Cold temperature starting requires an oil that will flow well at low temperatures. The higher engine temperatures of todays smaller, higher revving engines requires an oil that will perform well under high temperature conditions.

 

Pour Point Depressants

In order to improve the flow characteristics of a lubricant basestock at low temperatures additives called pour point depressants are used. Because synthetic basestocks have inherently better low temperature flow characteristics, pour point depressants are typically unnecessary. Therefore, they are normally only used in conjunction with petroleum basestock lubricants.

 

Waxy contaminants within petroleum basestocks tend to crystalize in low temperature conditions. These crystalized structures absorb oil and increase in size. This leads to oil thickening and poor low temperature flow characteristics. Pour point depressants do not inhibit this crystallization, as is thought by many. Instead, the pour point depressants are absorbed into the crystals instead of the oil, thereby lowering the volume of the crystals in proportion to the volume of the free flowing oil. This helps maintain the low temperature flow characteristics of the base oil even when crystallization occurs.

 

CHEMICAL ADDITIVES

Higher quality petroleum basestocks have less need for pour point depressants because they have lower levels of wax contamination. However, complete dewaxing of a petroleum basestock is not very economical, so all petroleum basestocks require at least some level of pour point depressant.

 

Viscosity Index Improvers

As a lubricant basestock is subjected to increasing temperatures it tends to lose its viscosity. In other words, it thins out. This leads to decreased engine protection and a higher likelihood of metal to metal contact. Therefore, if this viscosity loss can be minimized, the probability of unnecessary engine wear will be reduced.

 

This is where viscosity index (VI) improvers come in.

 

VI improvers are polymers that expand and contract with changes in temperature. At low temperatures they are very compact and affect the viscosity of a lubricant very little. But, at high temperatures these polymers "expand" into much larger long-chain polymers which significantly increase the viscosity of their host lubricant.

 

So, as the basestock loses viscosity with increases in temperature, VI improvers “fight back” against the viscosity drop by increasing their size. The higher the molecular weight of the polymers used, the better the power of "thickening" within the lubricant. Unfortunately, an increase in molecular weight also leads to an inherent instability of the polymers themselves. They become much more prone to shearing within an engine.

 

As these polymers are sheared back to lower molecular weight molecules, their effectiveness as a VI improver decreases. Unfortunately, because petroleum basestocks are so prone to viscosity loss at high temperatures, high molecular weight polymers must be used. Since these polymers are more prone to shearing than lower molecular weight polymers, petroleum oils tend to shear back very quickly. In other words, they lose their ability to maintain their viscosity at high temperatures.

 

Synthetic basestocks, on the other hand, are much less prone to viscosity loss at high temperatures. Therefore, lower molecular weight polymers may be used as VI improvers.

 

These polymers are less prone to shearing, so they are effective for a much longer period of time than the VI improvers used in petroleum oils. In other words, synthetic oils do not quickly lose their ability to maintain viscosity at high temperatures as petroleum oils do.

 

In fact, some synthetic basestocks are so stable at high temperatures they need NO VI improvers at all. Obviously, these basestocks will maintain their high temperature viscosities for a very long time since there are no VI improvers to break down.

 

MAINTAIN LUBRICANT STABILITY

 

Lubricating oils are not only prone to viscosity loss over time. They are also susceptible to breakdown due to contamination and/or oxidation which decreases the useful life of an oil. Additives are often used in order to inhibit the susceptibility of a basestock to this breakdown over time.

 

Detergents and Dispersants

Contamination due to sludge and varnish build-up within an oil can often be one of the limiting factors in determining the useful life of an oil. If this build-up can be minimized and contained, the life of the lubricating oil can be increased. Detergent and dispersant additives are utilized for this purpose.

There is some debate as to whether those additives considered to be detergents actually "clean" existing deposits, but at the very least they aid dispersants in keeping new deposits from forming. Detergent and dispersant additives are attracted to sludge and varnish contaminants within a lubricant. They then contain and suspend those particles so that they do not come together to form deposits. The more contamination within the oil, the more additive that is used up.

 

Since synthetic oils are less prone to leave sludge and varnish, these additives are used up much more slowly within a synthetic lubricant.

 

Some oils use ashless dispersants which are more effective at controlling sludge and varnish contamination than metallic dispersants. In addition, some ashless dispersants are actually long chain polymers that serve a dual purpose as VI improvers in multi-grade oils.

 

Detergents are all metallic in nature.

 

Anti-Foaming Agents

Although necessary for engine cleanliness, detergents and dispersants can have a negative effect on the lubricating fluid within your engine as well. Sometimes, these oil additives can play a part in oil foaming. In other words, air bubbles are produced within the oil. These air bubbles, if not neutralized, will reduce the lubricating qualities of the motor oil. Anti-foaming agents such as small amounts of silicone or other compounds are used to control this phenomenon.

 

Oxidation Inhibitors (antioxidants)

Oxidation inhibitors are additives that manage to reduce the tendency of an oil to oxidize (chemically react with oxygen). They are also called antioxidants.

 

The antioxidant reacts with the peroxides in the oil. These peroxides are involved in the process of oxidation. Reaction with the antioxidant removes them from the oxidation process, thereby lessening the chance of motor oil oxidation.

 

Oxidation inhibitors also serve one more very important purpose. They protect against bearing corrosion. Bearing corrosion is caused by acids within your motor oil. These acids come from combustion by-products, but they can also be the result of oxidation. So, by inhibiting motor oil oxidation, antioxidants also protect against bearing corrosion.

 

Corrosion Inhibitors

Although antioxidants prevent the acids caused by oxidation, they do nothing to neutralize the acids caused by combustion by-products. Therefore, other additives must be used in order to keep these acids in check and to protect engine components from their effects.

Some corrosion inhibitors are designed to protect non-ferrous metals by coating them so they cannot come in contact with acids within the oil. Other corrosion inhibitors are designed to actually neutralize the acids within the oil.

 

Anti-Wear Agents

Even with the best of oils there is always the possibility of metal to metal contact within an engine, however slight. Some oils (especially ester synthetics) will cling to metal surfaces better than others, but engines that are left to sit for any period of time may have very little lubricant protection at start-up.

 

This is especially true in cold conditions when petroleum oils do not pump well. To minimize the engine component wear caused by these situations, anti-wear additives are used. Additives such as zinc and phosphorus will actually coat metal surfaces forming a protective barrier against wear. They do not eliminate the metal to metal contact. They simply minimize the wear that occurs during those instances.

 

ALLEVIATE COMPATIBILITY ISSUES

Some additives are included in an oil to deal with compatibility issues between the oil and certain engine components. For instance, there are certain types of lubricant basestock that will cause seals and gaskets to swell or to shrink. These effects have to be minimized. Sometimes basestock blending will alleviate the issue, but in other cases additives might be used.

 

Depending upon the particular application the oil will be used for, some additives may be left out while others may be left in. For instance, in order to meet API SL fuel economy requirements, oils are now formulated with special friction modifiers. However, these friction modifiers can cause clutch slippage if used within motorcycle oils. So, motorcycle specific oils do not contain these friction modifier additives.

 

When considered as a whole, Engine oils are comprised mainly of basestock fluids. Only a small percentage of the oil is comprised of additive chemicals. However, addditives can play as important a role as the basestock fluid itself.

 

A high quality basestock blended with a cheap additive package will be poor oil. A high quality additive package added to a cheap basestock is no better.

 

Of course, a motor oil as a whole is far greater than the sum of its parts. In other words, even a high quality basestock combined with a high quality additive package isn't necessarily going to yield a great oil. The company manufacturing the oil has to know how to correctly blend those basestocks and additives so that they perform well together.

 

Cheers

Simon

Just a reminder that we're here to give advice and recommendations so please feel free to ask, we'd be more than happy to help.

 

Cheers

Simon

If you are "modding" your car and adding BHP then consider your oil choice carefully as the stock manufacturers recommended oil will not give you the protection that your engine requires.

 

A standard oil will not be thermally stable enough to cope with higher temperatures without "shearing" meaning that the oil will not give the same protection after a couple of thousand miles as it it when it was new.

 

Let’s start with the fundamentals. An engine is a device for converting fuel into motive power. Car enthusiasts get so deep into the details they lose sight of this!

 

To get more power, an engine must be modified such that it converts more fuel per minute into power than it did in standard form. To produce 6.6 million foot-pounds per minute of power (ie 200 BHP) a modern engine will burn about 0.5 litres of fuel per minute.(Equivalent to 18mpg at 120mph). So, to increase this output to 300BHP or 9.9 million foot-pounds per minute it must be modified to burn (in theory) 0.75 litres.

However, fuel efficiency often goes out of the window when power is the only consideration, so the true fuel burn will be rather more than 0.75 litres/min.

 

That’s the fundamental point, here’s the fundamental problem:

 

Less than 30% of the fuel (assuming it’s petrol) is converted to all those foot-pounds. The rest is thrown away as waste heat. True, most of it goes down the exhaust, but over 10% has to be eliminated from the engine internals, and the first line of defence is the oil.

 

More power means a bigger heat elimination problem. Every component runs hotter; For instance, piston crowns and rings will be running at 280-300C instead of a more normal 240-260C, so it is essential that the oil films on cylinder walls provide an efficient heat path to the block casting, and finally to the coolant.

 

Any breakdown or carbonisation of the oil will restrict the heat transfer area, leading to serious overheating.

 

A modern synthetic lubricant based on true temperature-resistant synthetics is essential for long-term reliability. At 250C+, a mineral or hydrocracked mineral oil, particularly a 5W/X or 10W/X grade, is surprisingly volatile, and an oil film around this temperature will be severely depleted by evaporation loss.

 

Back in the 1970s the solution was to use a thick oil, typically 20W/50; in the late1980s even 10W/60 grades were used. But in modern very high RPM engines with efficient high-delivery oil pumps thick oils waste power, and impede heat transfer in some situations.

 

A light viscosity good synthetic formulated for severe competition use is the logical and intelligent choice for the 21st century.

You must seriously consider a "true" synthetic for "shear stability" and the right level of protection.

 

Petroleum oils tend to have low resistance to “shearing” because petroleum oils are made with light weight basestocks to begin with, they tend to burn off easily in high temperature conditions which causes deposit formation and oil consumption.

 

As a result of excessive oil burning and susceptibility to shearing (as well as other factors) petroleum oils must be changed more frequently than synthetics.

 

True synthetic oils (PAO’s and Esters) contain basically no waxy contamination to cause crystallization and oil thickening at cold temperatures. In addition, synthetic basestocks do not thin out very much as temperatures increase. So, pour point depressants are unnecessary and higher viscosity basestock fluids can be used which will still meet the "W" requirements for pumpability.

 

Hence, little or no VI improver additive would need to be used to meet the sae 30, 40 or 50 classification while still meeting 0W or 5W requirements.

 

The end result is that very little shearing occurs within true synthetic oils because they are not "propped up" with viscosity index improvers. There simply is no place to shear back to. In fact, this is easy to prove by just comparing synthetic and petroleum oils of the same grade.

 

Of course, the obvious result is that your oil remains "in grade" for a much longer period of time for better engine protection and longer oil life.

 

If you would like advice then please feel free to ask.

 

Cheers

Simon

Go on then Oilman in your honest opinion in a nutshell what is the best Oil to put in a 300zx in this country that is modified to approx 450 bhp + Nitrous ?????

Go on then Oilman in your honest opinion in a nutshell what is the best Oil to put in a 300zx in this country that is modified to approx 450 bhp + Nitrous ?????

 

In my personal opinion the Silkolene Pro S 10w-50 ester based full synthetic. Esters assist the additive pack in a motor oil formulation because they are surface-active (electrostatically attracted to metal surfaces), so they help to reduce wear and friction.

 

They are fluid at very low temperatures and at high temperatures they are very chemically stable and have low volatility (don’t evaporate away).

 

They also help to prevent hardening and cracking of oil seals at high temperatures.

 

This is the same as I have recomended all along, and I would still stear clear of 10w-60.

 

Cheers.

Cheers buddy...

Hmm.

 

Quiet in here.

 

Cheers

Simon

Hi Simon

Been reading all your posts...great! :p

I've got a 10 year old Zed with 94k miles. I dont know what oil the previous owner put in. I read somewhere in this site that you shouldnt mix mineral and synthetic oils. Obviously I'll drain the old oil and change the filter. Something about one of the oils releasing all the sludge thats built up in the engine???

Oh yeah, do you know how mush engine oil the Zed takes??

Thanks Andrew

Hi Simon

Been reading all your posts...great! :p

I've got a 10 year old Zed with 94k miles. I dont know what oil the previous owner put in. I read somewhere in this site that you shouldnt mix mineral and synthetic oils. Obviously I'll drain the old oil and change the filter. Something about one of the oils releasing all the sludge thats built up in the engine???

Oh yeah, do you know how mush engine oil the Zed takes??

Thanks Andrew

 

Andrew,

 

You are right, you should not mix mineral and synthetic oil, this is because of the different addative packs contained within the oil, mixing them can cause them to react or cancal each other out.

 

For your car I would suggest a good quality PAO or Ester/PAO synthteic, these are known as true synthetics. Esters assist the additive pack in a motor oil formulation because they are surface-active (electrostatically attracted to metal surfaces), so they help to reduce wear and friction.

 

They are fluid at very low temperatures and at high temperatures they are very chemically stable and have low volatility (don’t evaporate away).

 

They also help to prevent hardening and cracking of oil seals at high temperatures.

 

Take a look at the Silkolene Pro S 10w-50

 

Tech specs here http://www.opieoils.co.uk/lubricants.htm

 

For a list of options and prices e-mail me a sales@opieoils.co.uk

 

Cheers

 

Simon.