Originally Posted by st24cossie
Most of the cossie specialists around the country many of who have raced these machine suggest to me mobil/castrol 15/50 or 20/60.
Much thicker than 5/40, due to the extreme temps in the turbo that would thin out lower rated oils too much??
Yes and no.
If you have very high temps you will need a 10w-50/15w-50.
The Castrol RS is mineral based and will shear down under hard use, a top quality ester/pao synthetic 5w-40/10w-50 will take more heat and punishment then a mineral based 10w-60.
Cheers
Guy.