Quote:
Originally Posted by 99LeCouch
...There's truly no such thing as a poor-quality SM-spec oil these days. ...
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There is definitely argument about that. A lot of people are claiming that the low levels of ZDDP mandated by the SM spec are actually damaging flat-tappet solid-lifter engines. The ZDDP (a zinc compound) is a high-pressure ant-wear additive, and has been reduced in the interest of lower Zn emissions. There is evidence that at least some older engines are wiping cam lobes and/or lifter faces due in large part to the smaller amounts of ZDDP in their oil.
It does not seem to be an issue with most modern engines, happily.
...I have also heard that Royal Purple is a very expensive oil that isn't very good. One Honda guy referred to it as "Purple Sludge".
-soD