NastySSoo

I was mixing 10w30 with 15w50 for a while, now Ive been using straight 15w50 in my 78k motor that sees weekly track use. Patman, do you really think i would be better off with 0w40? Everything seems good , and my oil pressure is not TOO high. I do find I see less smoke out the tailpipes with the 15w50. As you can see, I do live in fla.

Deeavi

iTrader: (16)

As long as you warm your engine up good before you run it! I have used 15W-50 in all my high performance cars until I bought my LS1. It is the best for hot weather and racing conditions, but an egine with tight clearences would probably benefit more from a thinner weight oil. Actually the Mobil1 0W-40 and the Amsoil 10W-40 make more horsepower and get better mileage than the 15W-50 oils. If you have ever primed an oil pump on an old small block chevy before that had 15W-50 in it it would stress the drill running the primer. It takes more horsepower to pump it! Especially cold!

stealth

Reher Morrison recommends 10W30 synthetic for my 622, so I use it, and Mobil recommends 15W50 synthetic for blown motors, so I use that. And I use 10W30 synthetic in my '99 SS street car.

But I do find it interesting that a 16:1, 622 BBC that revs to 8200 rpm uses a lighter weight oil than a blown 414 LS1.

Dope

iTrader: (2)

I'm running 10w30 redline in my H/C C5 (23k miles). Should I switch to 10W40? I run 0W40 Mobil 1 in the winter on my daily (98 SS), it works great, but I wanted a 5 or 10wX for the vette's summer use. I figured redline was probably thicker than mobil 1 so 10W30 would be fine.

Dope

Deeavi

iTrader: (16)

Why would you switch? You don't have that many miles on your car. I would stick with the 10W-30. The only reason I switched to a 10W-40 oil was because my car has 96,000 miles on it and I will use it Winter and Summer. That is why you buy multi viscosity oil. The new cars come with 5W-30 from the factory, so I would stay with 10W-30 or use the same 0W-40 oil as your SS.

There is alot of talk here about changing the type of oil you are running, but I am of the opinion, and I have heard other mechanics say that it is not good to be switching back and forth with different weight oils. Find one you like and stick with it!

Patman

To truly find out which viscosity you should be running in your particular application, the best thing to do is get an oil analysis done, and pay very close attention to the numbers for lead. If you're running a 10w30 oil and find the lead is too high, then that indicates you need to run something slightly thicker. Lead is an indicator of bearing wear.

Dope

iTrader: (2)

Hmmm good point. Patman: am I correct in my assumption that 10W30 redline is thicker than 10W30 mobil 1?

Dope

Patman

Yes, this is true. And Redline will also thicken up slightly as well.