lt1street

Is any body running a straight 40 wt oil like valvoline VR1 racing oil or does the mobil 1 ow30, ow40,ow50 the most common oil ran in the LT1??? And is it better (mobil 1).

slopokrodrigez

You don't have any power adder and have a stock bottom end. It doesn't matter what you use. You would be better off with stock recommended weight. If you have concerns about breakdown, use a synthetic. If you have a lot of miles on the seals and they leak with synthetic which occurs on a lot of older cars when switched, just add a swelling agent like Lucas oil treatment.

Remember, oils have progressed so far so fast that oils today are vastly superior to those used just 10 years ago.

Injuneer

You don't want to use a single weight 40 oil. It's not going to provide the required oil flow on cold start. That's when most of the engine wear takes place. The best thing to use in your car is EXACTLY what GM tells you to use, which is 5W-30. They also recommend 10W-30 in climates where the temperature does not go below 0degF.

If you use Mobil synthetic, consider the 0W-40, since tests have shown that the 5W-30 and 10W-30 have an actual viscosity that is slightly thinner than a true 30-weight oil.

You might want to try a "search" for posts by Patman. He has done a lot of oil testing in his 4th Gen, and can supply recommendations backed by facts and figures, not urban legend.