Re: Lack of Zinc in oil

Posted by Crazy Horse on October 07, 2017 at 07:54:06 from (75.159.240.214):

In Reply to: Lack of Zinc in oil posted by Mike Groom on October 06, 2017 at 16:36:08:

No shortage of info on the web, a lot of it makes sense, some of it is contradictory with other opinions. This little bit of info below sheds some light on the situation as it now stands ..... not that it solves anything but it makes some things a bit clearer. Take note of the "backward compatibility" information, and assuming that is is true, I doubt that many of us here are going to be affected too much using regular off-the-shelf oils in our older equipment. Now, if you are building high performance racing engines, etc ..... that's another kettle of fish. Anyways, a little knowledge is better than none I think, here ya go .....

"All the current gasoline categories (including the obsolete SH) have placed limitations on the phosphorus content for certain SAE viscosity grades (the xW-20, xW-30) due to the chemical poisoning that phosphorus has on catalytic converters. Phosphorus is a key anti-wear component in motor oil and is usually found in motor oil in the form of zinc dithiophosphate (ZDDP). Each new API category has placed successively lower phosphorus and zinc limits, and thus has created a controversial issue of obsolescent oils needed for older engines, especially engines with sliding (flat/cleave) tappets. API and ILSAC, which represents most of the world's major automobile/engine manufacturers, state API SM/ILSAC GF-4 is fully backwards compatible, and it is noted that one of the engine tests required for API SM, the Sequence IVA, is a sliding tappet design to test specifically for cam wear protection. Not everyone is in agreement with backwards compatibility, and in addition, there are special situations, such as "performance" engines or fully race built engines, where the engine protection requirements are above and beyond API/ILSAC requirements. Because of this, there are specialty oils out in the market place with higher than API allowed phosphorus levels. Most engines built before 1985 have the flat/cleave bearing style systems of construction, which is sensitive to reducing zinc and phosphorus. For example, in API SG rated oils, this was at the 1200-1300 ppm level for zinc and phosphorus, where the current SM is under 600 ppm. This reduction in anti-wear chemicals in oil has caused premature failures of camshafts and other high pressure bearings in many older automobiles and has been blamed for premature failure of the oil pump drive/cam position sensor gear that is meshed with camshaft gear in some modern engines."

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