10-15-2011, 12:21 PM
I hadda mechanic recommend I put Castrol GTX 20w50 in my LT1 with 147k miles. If it makes a difference I have headers and an air intake system on it. I hadda do an oil change anyways so I used his recommendation but with the viscosity I'm running at 70psi oil. Highest it'll go in acceleration is like 75. I'd been always running 10w30 and that always kept me at a comfortable 40psi. I see online people say you can and can't use it. I thought giving I have 147k miles I'd be okay but 70psi is making me uncomfortable. Should I switch back? I'd hate to make the engine work any harder.