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ZDDP - The Facts

Your classic car engine probably needs it

ZDDP (Zinc Dialkyl Dithio Phosphate)

"Experts don't all agree on what damage, if any, today's new oils with lower levels of ZDDP could be causing to older engines. While I haven't personally experienced any devastating engine failures from using motor oils made to new specifications, others state that they have, and the engine damage is disturbingly rapid and severe.
In the absence of more conclusive information, I would say that using a ZDDP additive at every oil change might be a wise decision for classic car owners. I can't promise that it alone will prevent engine damage, but it certainly wouldn't hurt, considering it is an important component now missing from new oils."

—Ken Wilson, Automotive Mileposts

Back in 2006, a new motor oil warranty category for gasoline engines was released. Designated GF-4, this new warranty specification was licensed by the American Petroleum Institute (API) and superseded all previous specifications. Historically, when a new specification such as this was released, all older cars built under a previous specification would be able to operate on the new one as well without any loss of lubricant protection, as the newer specifications normally provided at least the same level of protection as previous ones, and generally have provided improved protection as research developed newer and better detergents, additives, etc. However, that didn't happen in this instance, and it wasn't long before problems started being reported with engines in older cars.

For many decades all of the major oil companies used ZDDP (Zinc Dithiophosphate) in their motor oil formulations. ZDDP is an excellent anti-wear agent, and for years was inexpensive for the oil companies to purchase.

But along came catalytic converters, and everything began to change. When first introduced, catalytic converters contained things like platinum and palladium, which were expensive to buy, and have continued to become more expensive as the years have gone by. Due to this, the original equipment manufacturers (OEMs) changed the composition of catalytic converters to make them less costly. And with that change came the need to reduce the levels of sulfur, phosphorus, and zinc in motor oils because they will eventually destroy catalytic converters on new cars built with the new materials. When the EPA mandated that ZDDP be removed from all conventional and synthetic oils produced domestically that sought to meet the GF-4 specification, apparently no thought was given to what might happen to older engines that require ZDDP.

ZDDP protects older engines by creating a film on cams and flat lifter contact points. This film, consisting of zinc and phosphorus compounds, provides a sacrificial wear surface that protects the base metal of the cam and lifter from wear.

Additionally, ZDDP alters the surface characteristics of bearings and journals to prevent metal to metal contact, and reduces the tendency of critical engine components to scuff or gall under heavy loads.

There are a few motor oils on the market today that still have higher levels of zinc in them. One is Valvoline VR-1 Racing Motor Oil. It has been reformulated to meet all new car manufacturer's specifications, which means reduced levels of zinc. Some say it has enough zinc to protect older engines, while others say it falls short of what's needed to provide adequate protection.

There are additives on the market that can restore ZDDP levels to today's motor oils. One of them is ZDDPlus . Adding ZDDP Plus to every 4-5 quart oil change will protect your older engine from metal to metal contact, and restore the lubrication characteristics of new oil to the original specification for older engines, which will help to prevent the premature deterioration of critical internal engine components.

Until more is known about this issue, it might be wise for old car enthusiasts to err on the side of caution and add ZDDPlus at every oil change. We've even provided links on this page for you to order it now, and have it shipped to you, ready for your next oil change. Then when things get hot under the hood and you step on the gas, you'll know your engine has the lubrication protection it needs.

Click this link to buy ZDDPlus. It's also available on eBay, so if you're a member, you may prefer to buy it there. Links to active listings on eBay are provided below:



Click to buy ZDDPlus Oil Additive

(One bottle needed for every 4-5 quart oil change.)

Image: ZDDPlus

Compare to GM E.O.S. Engine Assembly Lubricant - ZDDP Plus has twice the amount of ZDDP!

ZDDPlus Oil Additive 4 fl. oz.

ZDDPlus Oil Additive - 3 pack (3 x 4 fl. oz. bottles)