I work on older model corvettes from the sixtys and seventys and have been told that the zinc additive in oil has been reduced, and in 2010 it will be eliminated. I am also told this is a concern with flat tappet motors as opposed to roller tappet motors. What should I consider when doing an oil change on one of these cars?
You are right to be concerned about the reduced zinc and phosphorus levels in the latest SM rated engine oils. The EPA is driving this in a quest to protect catalytic converters from carry over of these additives. Older flat tappet systems are better protected by higher levels of zinc and phosphorous anti-wear additives. In a pinch look for heavy duty diesel oils rated CI-4+ (not CJ-4). The best solution is to use an oil from Amsoil Synthetics that is high in zinc and phosphorus. Amsoil 10W-30 (ATM) or 10W-40 (AMO) are very high in zinc and phosphorus and are perfect for these flat tappet engines.
Dan Watson
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Dan Watson
Independent AMSOIL Dealer
