A short lesson on Multigrades:

 

If you see an expression such as 10W-40, the oil is a multigrade.

 

This simply means that the oil falls into 2 viscosity grades, in this case 10W & 40.

 

This is made possible by the inclusion of a polymer, a component which slows down the rate of thinning as the oil warms up and slows down the rate of thickening as the oil cools down.

 

It was first developed some 50 years ago to avoid the routine of using a thinner oil in winter and a thicker oil in summer.

 

For a 10w-40 to attain the specification target a 10W ( W = winter) the oil must have a certain maximum viscosity at low temperature. The actual viscosity and the temperature vary with the viscosity grade but in all cases the lower the number, the thinner the oil, e.g. a 5W oil is thinner than a 10W oil at temperatures encountered in UK winter conditions.

 

This is important because a thinner oil will circulate faster on cold start, affording better engine protection.

 

For a 10w-40 to attain the other specification target a 40 oil must fall within certain limits at 100 degC. In this case the temperature target does not vary with the viscosity grade, if there is no "W", the measuring temperature is always 100degC. Again the lower the number the thinner the oil, a 30 oil is thinner than a 40 oil at 100 degC., which is typical of maximum bulk oil temperatures in an operating engine.

 

The engine makers are, of course, very well aware of this and specify oils according to engine design features, oil pump capacities, manufacturing tolerances, ambient temperature conditions etc. It is important to follow these guidelines, they are important and are an are stipulated for good reasons.

 

If the engine has been modified, the operating conditions may well be outside the original design envelope. The stress on the oil caused by increased maximum revs, power output and temperature may indicate that oil of a different type and viscosity grade would be beneficial.

 

Cheers

Simon

Simon

 

...thanks for that. Always good to get specific info. What we need (as a club) is a recommended matrix of oil specs for the NA's and TT's in say 2 stages of tune? ...and in summer and winter? ...maybe usage as well.

 

Asking too much?

 

Cheerz

 

Jack

No mate we can do that for you.

 

Normally an Oil and Recomendations thread as a sticky works, that way all the questions are in one place, over time it turns into an FAQ as it will end up covering most specs, state of tune and use.

 

Cheers

 

Simon.

I think I already posted something along those lines a while back.

 

Basics are as follows really:

 

In stock road cars 5w-40 or 10w-40 semi or fully synthetic

 

Semi changed every 4000-6000 max, fully every 8000-10000 max.

 

If the car is modded or used on track then a good quality race synthetic is a wise option but following these oil temp guidelines.

 

Up to 120degC 5w-40 or 10w-40

Over 120degC 10w-50 or 15w-50

 

Cheers

Simon

Simon - again, thanks for this - I wasn't sure if I'd seen the recommendation before.. short memory.

 

Would you recommend the same for both NA and TT?

 

many thanks

 

Jack