10-40 or 20-50 oil ???

[Bernica]

Originally Posted by Bob Broberg SPF667 460BB

Dan, everyone is going to have a favorite viscosity. If you are not racing, you probably don't need the 50 weight when hot and most new cars with high hp have narrower clearances in their engines so 5 or 10 weight when cold is preferred. Since most cobra owners change their oil often you also probably don't need synthetic. I have 62K+ miles on my motor and I simply use name brand whatever is on sale with ranges of 5-20 to 10-40 (if racing) but mostly 30w or 10-30. Don't "play" until oil temp is off the pin and check it every time before you use it. I add an oil treatment with Zinc, like STP the first time my level is down 1/2 quart.
My motor was setup one the "loose" side for endurance and still has good compression but uses some oil when I play too much at high rpm. Which is rare now.

AZ Bob

My clearances are as follows and I am running Joe Gibbs XP3. It's already got the zinc in it. Pressure starts high and settles at around 50-60 after warm up. Fluctuates but never below 40, which is my worry point.

Mains: .0022-.0025
Piston to wall: .004
Rods: .0025-.0030

[1985 CCX]

High Zinc content #1;
second typically 5-40 for me

[Bernica]

Originally Posted by 1985 CCX

High Zinc content #1;
second typically 5-40 for me

So, the XP3 I am running equates to 10-30. With my clearances, does that sound right?
See? Now you have me second guessing myself!