Patman

An even better oil than that is the Delvac 1 5w40 by Mobil 1, this oil is used a lot by fleet owners, it's a very long drain oil that stays in grade very long and shows excellent oil analysis results. Some consider it Mobil 1's very best oil.

SSDude

Hey Patman,

I was under the impression that 5W20 was too thin to use especially in warm weather. If I use Redlilne 5W20 will it harm my car in the summer month.

Patman

It's true, it might just be too thin for the LS1, which is why it would take someone who is very open to experimenting in order to try this thin oil, and only if they do oil analysis to see how it goes. Every engine has a certain "sweet spot" as far as viscosity goes, and so oil analysis is the best way to determine this. I have a strong feeling the LS1 prefers something closer to a high 30wt to low 40wt oil. But at the same time, different examples of the same engine could vary also, as a higher mileage engine will typically need a slightly thicker oil since it's clearances become slightly bigger.