I honestly wouldnt worry about going to a higher weight oil unless your either:

1 using the car as a race only vehicle. (which is so far from stock that the only thing stock about it is the GM decal you put on the front of the cars aero package)

2 have a high millage engine of over 50K

3 are in a area where the temperature averages above 110 degrees

Your using a synthetic oil that is very resistant to breaking down form high temperatures straight form the factory. Watch your oil pressure after running the car for about 30 min or at the end of the drag strip. if at idle your getting less than 20psi then changing to a higher viscosity -MIGHT- be a good idea. I say thsi because of teh tighter specifications that engine makers have with new engines.As a matter of fact the Police variation for the Ford Crown Vic runs on 5W-20. Those engines routinely have that oil added to them well past the 100k mark and run just fine.


I had a case where a tech in a bay over put 5-30 in the engine and the car came back a week later with oil consumption problems. The thicker oil caused seals to fail due to a raise in the oil pressure.

If your going to run thicker oil that's fine, but be very careful. Running something like 20W-50 is to be honest unnecicary and possible damaging.. That's oil intended for a diesel engine that runs 24 7 without a break in the summer.

Note Amsoil doenst' have RP, Motul, Greddy, Brisk, or any other exotic racing oils in that test.

Not to say Amsoil isn't great oil, it is. It's just in that comparison they are like a major league baseball player playing against a bunch of 12 year olds.