Quote: I agree with the excessive stp deal. 3 in a burned out /6 maybe... The only additive you may need is zinc, and there are better versions of it out there now.
I put my engine into an "extreme over-rev" condition in the spring and it bent # 5+6 exh valves.
What is it about STP? Is it the thickness that is to much and causing the bearings to spin? I used it in an engine for a while that had bearing wear and low oil pressure and it bought me another year.
But I would think too high a viscosity could be a problem, no?
