oil api rating SH vs SM

Wanted opinions on oil for V6 and V8 Buicks.

Found some SJ,SH 4-cycle hd sae 30 Quaker State oil at Menards.

Would SJ,SH rated oil be better for our Buicks than the new SM rated oil?


Will be adding ZDDP additive with either oil.




This is copied from a motorcycle blog ( makes the SM oil sound really bad for engines)

API Oil Standards

The additive package is made to make the finished oil product meet one of the certifications. There are two classes of certification: S, for Service, and C, for commercial. The certification standards are maintained by the API, the American Petroleum Institute. Over the years, the API has improved and changed these standards. The most current S standards are SL and SM. These standards differ from earlier standards like SH by lowering phosphorus to improve catalytic converter life, and increasing molybdenum to lower internal engine friction and improve gas mileage. Phosphorus was originally added to oils to help protect high pressure areas like cam lobes and crankshaft bearings, so lowering phosphorus levels is a compromise of lower pollution, perhaps at the expense of engine life. Molybdenum is added to improve fuel economy due to the federal CAFE (Corporate Average Fuel Economy) standards, thereby helping GM and Ford keep selling large V8s to the American public, but can perhaps cause problems in engines with wet clutches. Most S additive packages are also designed to be inexpensive so that the resulting oil can be sold at a low price. SL and SM oils are both low phosphorus; SM oils which are labeled "energy conserving" are high molybdenum.
About every three years or so, the API releases a new S standard. The new standard supercedes the old standard, so, for example, the SH standard included extra high temperature deposit protection due to the popularity of turbo engines in the early '90s; SJ oils did not have this high temperature protection, as that portion of the standard was dropped. This means that for some cars, oils made to the older rating systems are sometimes better than oils made to the new standards. SH certified oils are probably the best of the S oils for motorcycles and high- performance sports cars, but you pretty much can't buy them anymore. Oils which are labeled "energy conserving" are bad for any vehicle with a wet clutch, meaning most motorcycles. Essentially all 0w-20, 5w-30, and 10w-30 oils are energy conserving and should not be used in your bike.
Most people blending S type automotive oils are buying their base oils from a company who is most likely using the Chevron Iso- DeWaxing process to make their oils, then buying their additive package from another company that is highly constrained by the API standards. The cost of getting an API certification for a single S motor oil formulation is from $125,000 to $300,000. The cost for C certification is $275,000 to $500,000. Once testing is complete, the oil can be licensed for $825 per year, plus a small royalty fee per gallon sold for all gallons over one million. The length of time between new specifications is now approximately 2 to 3 years, which does not allow a great deal of time to recover testing costs.
Additive companies, such as Lubrizol, Ethyl, Infinium and Oronite develop licensed additive formulas that they offer to oil companies to re-license. It is inexpensive to re-license one of these formulas, and the majority of oil companies choose to do this to avoid the costs associated with testing. Thus, the same chemistry is being sold under many brand names. Because of this, S type automotive oils have pretty much turned into a commodity. Although the people selling a particular brand may wish you to believe their oil is superior to any other, in fact if it's got the API seal on it, it's probably about the same as any other similarly rated automotive oil.


Wish I stocked up on cases of the old Rotella a few years ago.

Al