I'm running Mobile1 15k-15-50 in my 97z with 78k on it. Think that's too heavy? Also just got a brand new 2006 GTO last month and thinking that the mobile 1 5-30 is too thin for the ls2. What do you guys think?

 

I wouldnt run a 15-50 in my car ...

I use M1 5W-30. And if you look into it, alot of people the Castrol Syntec (**** that is German Made, not the American stuff) 0W30 shows the best used oil analysiss on the stock shortblock.

However, If you look at what some of the engien builders say, (Such as Bret) they have seen the best bearing conditions and such with alot of cars run on M1 5W30.

 

I think unless you have gotten specific instructions from an engine builder to use any weight oil other than what is in the owner's manual you are potentially damaging the motor. The tolerances on newer engines are so precise due to manufacturing quality that heavy oil does not get to the places it needs to be, even in an engine with 80k miles. The exception is an engine with genuinely low oil pressure.

 

That is way too heavy for a street car.

Rich

 

You're wasting power and overworking the somewhat flimsy LT1 oil pump drive setup.

Why do you feel 5W-30 is too light for an LS2? Figure the GM engineers are complete incompetents?