Reply to SJ:
Boy some of these nutty people down there have got so technical they are dangerous to us all & want to tear this country apart & it will in time.
The obsolescence plan has already started😠😠ðŸ˜
The latest API Service designation (SM) has cut way back on one of the former lube contents known as ZDDP (zinc dialkyl dithiophosphate) who's sole purpose was/is to provide lubrication for camshafts and lifters as an extreme pressure lubricant in conjunction with molybdenum disulfide. Apparently the ZDDP contaminates catalytic converters and is on the way out. The SM designation has about half the required 1200 parts per million ZDDP required for vintage engines. If you can still get the SG, SH, SL, designated oil your ok but the SM requires additives be added to the oil.
The two suggested in this article are:
Camshaft and lifter prelube GM part #12345501 (4-oz bottle)
Engine oil supplement GM part #1052367 (16-oz bottle)
I'm sure there are others.
Suggested dosage is two ounces per quart of SM-rated oil.
I'd also recommend you take up the discussion with your oil supplier.