Comp Cams had a news letter on their web site a couple of months back discussing premature cam failure. They talked about proper startup and break in, etc, etc but also discussed recent changes to
oil formulations, specifically the reduced level of
zinc. I did some searching and the additive that has been reduced is referred to as ZDDP which is
zinc dialkyl dithiophosphate. The EPA has mandated a reduction in this additive.
Most modern engines have overhead cams so there is a much reduced friction between the cam and the lifters, many of which are now rollers. Therefore this reformulation does not hurt OHC engines. However, high performance pushrod engines exert lots of pressure on the cam and the flat tappet lifters and this is where the ZDDP is required.
Comp Cam goes on to say that they recommend oils such as Shell Rotella T, as well as some of their own additives.
Simply out of curiousity, I contacted STP and was advised that the main ingredient in STP
oil treatment is ZDDP. While I have not used STP for many years, I will probably now begin to use a can of it with each
oil change.
A friend of mine who is an engine builder, has had several cam failures during the past year, which very rarely happened previously. He now will not guarantee an engine equipped with a flat tappet cam if the customer uses any oil other than Shell Rotella T. He gives a copy of the Comp Cam news letter to every customer so that they have a better understanding about the recent changes to motor oils.
Wayne