Another Oil question (0w20)

[Richyvrlimited]

I've recently purchased a GT86, and was rather surprised that the recommended spec of oil for the engine was 0w20 (or 5w30 - but if you use 5w30, it should be changed to 0w20 at the next service).

AIUI the number after the w indicates the viscosicy under load / at higher temps, and generally the higher the better, (as long as it's not a large distance from the 1st number as that indicates lots of additives which will degrade).

I also was under the impression that if it's a boosted or high revving engine you should have a higher right hand number i.e.40 or 50.

The GT86 is relatively high revving, 7.5k redline and I'm someone who likes to rev a car, I also like to track the car.

So should I stick with the manufacturer specification oil, or change to something else?

Cheers

[Richyvrlimited]

HustleRussell said:

Yeah, put whatever right hand number sounds nice to you, so long as it's not too far from the left hand number !!!1!

Silly Toyota telling us to put little right hand number oil in when 40 or 50 right hand number definitely sounds more familiar and also bigger?

Did you get out of the wrong side of bed this morning or something?

A larger difference between the cold and hot viscocities requires more, (long chain I think), additives which when the oil is subjected to extreme temps/pressures break down.

My old car (MX5 obviously), had an OEM spec of 10w30, but the engine performed much better with a 0w40. This is why I'm asking about possibly defiating from the manufactures recommendation.

[Richyvrlimited]

PaulKemp said:

Hey it's your car, if you want to gamble with an expensive engine, carry on.
Just let us know when it goes wrong so we can learn by your mistake
If it doesn't strip it down and measure the wear so we can compare your engine to one with servicing to the manufacturers specification.

Jesus wept,

I don't want to gamble, that's why I'm asking.

[Richyvrlimited]

one eyed mick said:

Do you really think that manufacturers and oil companies would specify incorrect oil for millions of cars ? If so get the next bus back to earth asap

Get over yourself and read puma's reply.

The OEMs pick an oil type for many reasons, not necessarily to protect the engine to last 200k+

[Richyvrlimited]

Pumaracing said:

I could have sworn I covered all this not long ago but can't remember which thread. In a perfect world engine oil would have the same viscosity at any temperature - the one single viscosity that produces the ideal oil pressure for the pump system and bearing clearances in a given engine.

In the real world fluids get less viscous as temperature increases and no amount of long chain polymer additives can compensate for this. EVERY multigrade oil ever made is too thick when it's cold - end of. Even a 0-30 is far too thick when it's cold. So forget the first number in a multigrade other than it can never be too small. Something like a -30 would be nice.

The second number, the hot viscosity, is the one to worry about and IMO you can't really beat a 30. You certainly never need anything thicker in an unworn modern engine and I still believe that anything thinner is more about fuel economy than engine protection.

Thanks for the technical response, this was the sort of reply I was after, then I could make some form of informed opinion.

If we all did what the manufacturer though best, no one would modify their cars at all....

[Richyvrlimited]

Thanks again all, that's really good to know.

That article steveturbo posted was fascinating.