Which oil? Mineral vs Synthetic

[threewood]

I have a small stash of Valvoline VR1 10w30 that I use. Synthetic. This has a shorter time between changes as it does not have the cleaners added to it so it gets dirty faster.

My large stash is Driven HR2 10w30 conventional oil.

I use both in my 318 Poly solid lifters and my 440 solid lifters. Average clearances.

 

[Geoff 2]

Very foolish adding any thing to today's oils. Additives like STP & Zinc go back decades. Oils today are not the same. The additives that the manufacturer selects are carefully blended to work together, not against, each other for superior protection.