15w-40

[1929]

Originally Posted by Seth Swoboda

Patrick has it correct. 15-40 Shell Rotella is perfectly acceptable to run in your Model A and any other flathead engine you may have. It does have a zinc additive that is very friendly to your Model A engine.

I was given a bottle of ZDDPlus, the rebuilder said to add to the oil because it restores the zinc and phosphorus levels in the oil and is needed for flat tappet cam engines.