NZR Petrol octane rating

[Smithy]

If i wanted to have a sample of petrol tested for it's octane rating, anyone know how i'd go about it ??

cheers

smithy

[Uno]

Paul...saw this and copied from the web...HTH

 

RON, MON or PON?

Or how do you grade petrol/gas

I have seen many European/US conversations claiming that one petrol/gas is better than another or higher rated. This may not be the case as different rating systems are used in different countries and so not all numbers mean the same thing. You must be careful to also quote the measurement system used

 

To see why there are different numbers let us take a trip back in time to World War I. Aviators had a problem, many engines would suddenly self destruct through detonation, which is bad news when you're up in the air. An engine might run fine on one batch of fuel but blow holes in the pistons on the next batch. The fuels seemed the same, weighed the same and may have even come from the same factory.

 

The fuel companies tried to analysis and standardise the petrol, but were unable to weed out the bad batches. Therefore a standard test engine with a variable compression facility was built and the fuel to be tested run through it. This heavy duty, single cylinder engine would be warmed to a standard temperature and at a set rpm the compression increased until engine knock occurred. this would give its Highest Usable Compression Ratio (HUCR).

 

But with time it was discovered that different labs gave different results. So in an attempt to produce an unvarying standard, two reference fuels were chosen. The high reference was 2-2-4 trimethylpentane (iso-octane), while the low reference was normal heptane (n-heptane). Once the HUCR was determined a mix of these to fuels was made up that exactly produced the same results as the HUCR test. The result is quoted as the percentage of iso-octane. Hence a petrol that detonated the same as a mix of 90% iso-octane and 10% n-heptane is called a 90 octane fuel.

 

Since that time a number of tests have come into being to simulate a variety of engine conditions. Motor Spirit is usually rated using the Research or Motor test methods. Both use the same old engine but under different conditions

 

Motor Octane Test (MON) Research Octane Test (RON)

Inlet air temperature 148.9 C 65.6 C

Engine jacket temp 100 C 100 C

Engine RPM 900 600

 

As you can see the Motor Octane Test employs a higher temperature and RPM and hence is probably a better indicator for today's engines. Of course the Research octane test gives a higher number and that's why the European manufacturers quote it (RON)

 

The spread between the two numbers is know as the fuels sensitivity, and it is very important. Because of the variety of engines it is possible for a petrol manufacturer to come up with a fuel that has a high RON, but a lower than expected MON. Hence although it looks normal on the pump it may perform badly. However on another day the same company may make its fuel out of a different blend to get the same RON but a different MON. This is done for profit reasons and is why you occasionally get bad fuel even though it is legally rated the same. In the past with high leaded fuels nobody noticed but nowadays high performance cars do notice (The Molemobile has just had a particularly bad batch from Total, and has been pinking all week)

 

In America the service stations use the Pump Octane Number or PON rather than RON. this is the average of RON and MON and gives a much better grade, and is also why the American gas always seems not as good as our when in fact it is is the same (and has better quality control). But even this system can be abused by adding octane boosters to poor fuel.

 

Below is an approximate comparison chart, these numbers can vary by as much as 2 grades

 

RON MON PON

90 83 86.6

92 85 88.5

95 87 91

96 88 92

98 90 94

100 91.5 95.8

105 95 100

110 99 104.5

 

So now you know far more you wanted to about RON, MON and PON. Knowing this you might begin to wonder why certain garages are always cheaper than others, and experiment with different fuels. I'm lucky, my new job has just given me a fuel card for private use, so I'm moving up to super unleaded, that way I can be assured I'm getting at least 95 RON

[znut]

who needs the discovery channel when you got this forum

[Smithy]

Cheers for all the info mate, don't suspose you found anywhere though who takes a sample of fuel of yer and tests the "Ron" rating ??

ta

smithy

[Guest andyduff]

The way I understood it was it'll need to be run on one of the variable compression test engines. You'd need a fairly large sample I'd have thought to get any results though.

[Uno]

there are some handheld octane readers...use 8oz of petrol...cost will set u back??

 

see here..http://www.geneq.com/catalog/en/poa.html

 

cheers

[Rich666]

Cheers for all the info mate, don't suspose you found anywhere though who takes a sample of fuel of yer and tests the "Ron" rating ??

ta

smithy

 

Guessing your reasons... trading standards may be a useful reference point...

 

Only problem is apparently (think someone mentioned on here) there are tolerances for their storage tanks - i.e. if the tanker begins discharging into the wrong tank, they leave it in as long as it's below a set percentage - providing a pretty good get out clause if the station gets caught out!

 

Rich

[DTA (UK)]

And on a slightly related note: from which point does the pump meter measure the amount of petrol you're pumping into your car? Is it at the nozzle or inside the pump? If the latter then we're getting ripped off as there will be some petrol left in the hose and nozzle ...

 

Good luck Smithy in getting the octane tested ... I'd be very interested what the actual octane rating difference is between Shell Optimax and BP Ultimate. Both claim to be 98 rated but as stated above, this could mean different things ...

 

CheerZ!

 

Dan

 

PS : Paul - it was good to catch up with you at the AutoSport International Show last Friday. Sorry I didn't phone before I left the show but I had to go back into work quite unexpectedly.

[MAC 1]

On another slightly related note.I know someone that uses avaiation fuel mixed with unleaded for drag racing,although it has nothing to do with testing what ron;)

[znut]

On another slightly related note.I know someone that uses avaiation fuel mixed with unleaded for drag racing,although it has nothing to do with testing what ron;)

 

that reminds me of when i was into bikes and a close mate use to work at a local airport,we use to run our bikes on avgas,i think its 115ron. good ole days

avgas+gsxr1100+190 section rear track tryes+no fear=FUN

[Guest mickeyb]

And on a slightly related note: from which point does the pump meter measure the amount of petrol you're pumping into your car? Is it at the nozzle or inside the pump? If the latter then we're getting ripped off as there will be some petrol left in the hose and nozzle ...

 

But the same amount of fuel would have been left by the previous person that used the pump. Therefore you still get the amout that you pay for...

[DTA (UK)]

But the same amount of fuel would have been left by the previous person that used the pump. Therefore you still get the amout that you pay for...

 

Fair point ... unless your the sod after me because I try and tip the remainder all out into the tank ;) Anal ... I know ... but there you go!

 

Dan

[Guest andyduff]

And pretty pointless too - the nozzle is the valve LOL so all you're getting is the bit in the short spout after the end ;) Just buy a Diesel Danny :rofl: ;)

[DTA (UK)]

And pretty pointless too - the nozzle is the valve LOL so all you're getting is the bit in the short spout after the end ;) Just buy a Diesel Danny :rofl: ;)

 

Actually not a bad idea Andy! Had the privilege of "delivering" a new Audi A8 diesel - you wouldn't know it was an oil burner from driving it! Excellent car and if I had the dosh I'd seriously consider one. Damn - did I just think this out loud? ;)