Just about everything on the market now, except for high mileage & diesel oil, is SM.
The way I understand it, SM has less ZDDP than SL, but better base stocks. I don't know what the oil makers use to make up for the lack of ZDDP.
Ya, last time I bought 4 cases 0f HondaGenuine 5-20 for $1.75 qt. ...I go back to the same dealer and he says $3.50 qt. list price now, but only $2.75 for me...so I walked away from the goof...stopped at AutoZone and the XOM Superflo 5-20 was $1.77 (didn't look for SM mark) but someone here said it goes for as little as .88 cents? really? We should start a "whats on sale now" thread....eh?
For our ATV's (5 of them) I just paid $108.00 for a case of Amsoil 20-50 MCV...WHEW!
quote: The way I understand it, SM has less ZDDP than SL, but better base stocks.
It's amazing how the base stocks can continually get better. Just imagine how comparatively bad the base stocks must have been 15 years ago. Good that with oil it's not like with product X on the tv: "New and improved" and the ever-popular "New look - same great taste."
As recently as ten years ago, conventional motor oil consisted of what amounted to Group I solvent de-waxed base oils and shear and oxidation-prone VII polymers. The rest of the additive package was reasonably formulated. Current energy efficient motor oils are at least Group II, with many adding Group II+ or Group III to the mix and much more shear and oxidation-resistant VII polymers. Per automaker concerns, SM rated motor oils have dropped the ZDDP content (and there'll be another drop in the upcoming SN designation in a couple of years), but molybdenum is an increasingly popular makeup compound, though there are other compounds equally or more effective - usually more expensive. There was never anything remotely superior or unique about ZDDP other than it was both effective and C-H-E-A-P. The above poster's cynicism aside, current conventional oils <i>are</i> considerably improved over what was previously offered. Personally, I'd go so far as to prognosticate that SM motor oils were just what sludge-prone Toyota motors <i>needed</i> from ~1996 - 2002.
I mostly agree with what Ray H said.
But it seems like SM mostly brought dino oils and synthetic blends up to much better standards. From what I understand most of the better synthetics Group III on up were already capable of passing SM standards, except in the area in reduction in zinc ect. From what I understand many SJ dino oils still could have used some Group I in the basic formula.
Some Toyota's, Volkswagens, Chrysler, Audi, and Saab have had documented issues with oil sludging as late as 2003 models.
Link to sludge problem