To comply with EPA exhaust emission requirements, the levels of the EP (extreme pressure) additive ZDDP (zinc dialkyldithiophosphate) in today’s oils have been drastically reduced. This is fine for modern roller lifter engines but for our flat tappet engines it spells disaster. The zinc and phosphorus in ZDDP creates a film on the cam and lifter that protects it from wear. Without this protective film the cam and lifters will wear prematurely.
One 4 oz. Bottle of ZDDPlus added to a 5 quart oil change contains enough ZDDP to give 0.18% zinc and 0.13% phosphorus level that was present in oils prior to the EPA reductions.
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