The Stovebolt Site Forums The Shop Area Engine Shop oil recommendation

Regarding ZDDP, how much is enough? I suppose that depends on valve spring pressure and cam lift rates, both of which are low on a Stovebolt.

Straight 30 is heavier than what GM specified back in the day, IIRC it was 20/20W.

I've run much heavier oils than that in mine with no apparent problems, like say, 20/50 but with the 6V battery the starter didn't like to start it in winter. So I switched to DELO 15/40, that I got for free from draining the compartments of the tankers I drove before the next load. Otherwise it went in the transmix tank to go back to the refinery at the company's expense. When I retired I had about 20 gal. of DELO. That's all gone now so I have to buy the stuff. I got over 200K out of the 235 before it burnt a piston so DELO must have been OK. But since I retired in 08 they cut the ZDDP in DELO. So now I'm at the mercy of the oil flame wars.