what off the shelf engine oil ?

From my vast research on the hot subject.
1. Diesel oil has more detergent than necessary for a gas engine.
2. Racing oil doesn't have enough to hold contaminates in suspension, which means change it more frequently.
(Unless you burn or leak it like my driver. In which case just add to it till the change. Because I got a lifetime supply of the synthetic stuff on closeout at Advance)
3. STP has zinc.
For what it's worth. I've got a 86 318 cop motor with almost 200K on it. I've run Mobile One for years in it.
And you can read anything on the internet.