Thread: Oil questions
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Old 04-05-2014, 05:15 AM
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Folks get very sensitive about their oil brands, and I'm not going to get into that discussion.

The most common antiwear additives used in engines are zinc dialkyldithiophosphates (ZDDPs), which have the chemical formula Zn[S2P(OR)2]2, where R is an alkyl group. ZDDPs have successfully been used for over 60 years, and to date no superior antiwear additive has been developed for use on steel.

ZDDP has an excellent track record at protecting the sliding metal-to-metal cam lifter interface. Historically, ZDDP has been added to oils in amounts resulting in approximately 0.15% phosphorus and 0.18% zinc.

ZDDP protects by creating a film on cams and flat lifter contact points in response to the extreme pressure and heat at the contact point. The film of zinc and phosphorus so formed provides a sacrificial wear surface protecting the base metal of the cam and lifter from wear. In the course of normal service, this conversion of ZDDP to elemental zinc and phosphorus depletes the ZDDP level in the oil.

Synthetic oils are excellent for not breaking down under high temperatures. That is what they were designed for, not better lubrication. So, if your engine has no turbo charger heat, you're wasting money on high temp oil.

ZDDP has been removed from common engine oil because it attacks your catalytic converter, and modern engines do not have flat tappets, so they really don't need ZDDP. Classic cars DO. When our engines were designed in the 1950s and 60s, oil formulation contained lots of ZDDP and it did a good job of lubricating.

The internet is full of good info about our classic car engines of every brand. We're all in the same boat. The only ones quiet about ZDDP levels are the oil companies. They really don't want you to know current levels in their modern oils, and to search for hard facts is like pulling teeth. I recently asked an STP rep what the levels were in his oil treatment products. He said, the ZDDP levels were more than we need, but he refused to give me any numbers. All I know is, many products that used to have high ZDDP levels are gone, now. They were either reformulated or were taken off the market.

Again, oils with '40' or more in the numbers or 'racing' oils are most likely to have 1,000 (or more) ppm ZDDP.

Protect your engine by researching current ZDDP levels in the oil you use. Find the real facts. If your oil simply doesn't give ZDDP levels, find oil that does. I had a cam wear out and I know this is a real problem: At first, much of the power was lost. Soon after, the rocker arms barely moved the valves. Buying a new cam puts you right back in the same situation all over again.

I change my Rotella-T oil every 3,000 miles because the ZDDP is sacrificial, not because the oil looks dirty. - Dave
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