FAQ about ZDDP Oil Additives & Cam Lube


The EPA has put stricter emission requirements on new cars that influenced manufacturers to remove ZDDP from motor oils. If you have an older car that was specified to use SF (1988) or earlier motor oil, its design requires ZDDP. Your older performance car could be damaged with the use of modern SM oils prevalent today. Cars equipped with flat tappet cams need ZDDP because of the high-pressure points. Newer cars have roller rockers and ZDDP is not needed in those applications.

In the API (American Petroleum Institute) classification system, “S” and “C” are the two basic application categories of oil. “S” is intended for gasoline use and “C” is intended for diesel use.

“A” was the first grade in each category and resulted in “SA” and “CA” grade oils. Each designation progressed farther up the alphabet as new grades of oil were introduced. The newest grades are “SM” and “CJ” respectively. “SF” was for 1988 and older engines.

Historically, every new grade of oil introduced since the 1930’s was better than the previous grade and could be considered “improved” with one exception. The original SA grade was straight mineral oil (non-detergent non-additives) and SB contained additives which could not be used in the earliest cars specified for SA. While it is true that SM oils are better for NEW cars, they are NOT better for the OLDER cars equipped with flat tappet camshafts. Simply put, the newer, better oils are not backward compatible for older cars primarily due to the gradual reduction of ZDDP starting with SG grade introduced in 1988. In the next few years, it will be eliminated completely from oil.
One bottle of ZDDPlus™ will raise the ZDDP concentration level of SL or SM oil to the standards that were in place when SF (or earlier) oil was specified. (SL and SM is the current category available today).
ZDDP is most effective if the concentration is between 0.18 and 0.2 % by weight. Tests have shown that concentrations above this amount, up to as much as several percent, have no effect except to prolong additive life. The current oils available today contain very little ZDDP.
Yes, ZDDPlus™ should be compatible with all conventional and synthetic oils intended for automotive use. Virtually all of these current oils have had some amounts of ZDDP for years, and it continues to be decreased in available oils.
The shelf life of ZDDPlus™ is essentially the same as regular motor oil (many years), as long as a few conditions are met. The temperature should be kept below 120 degrees F and above 0 degrees. You need to keep it sealed until it is mixed with motor oil. ZDDPlus™ has a tendency to absorb moisture, not unlike brake fluid. Absorption of water will degrade its performance, although heating it above 100C until it is not cloudy will restore it.
Anytime, but the best time is when you get the oil changed. A single 4-oz bottle is the correct concentration for a 4- to 5-quart oil change. This will bring the oil back to SF specifications.
ZDDPlus™ is a sacrificial additive, meaning that in the process of working, it is depleted. ZDDPlus™ should last the life of a normal oil change as specified by the manufacturer of the car, but attention should be given to the categories of service known as “normal” and “severe” conditions. Severe includes stop-and-go driving and short trips, which result in shortened service life of not only ZDDPlus™ , but most of the other additives in the oil.
The general public, as a rule, has nothing to be concerned about. The people that need to be concerned are owners of older classic cars and performance cars. After the SF category, the amount of ZDDP has gradually been reduced as each new API category is introduced. Had ZDDP been removed completely after 1988 (SF), the scramble for an alternative would have been a big concern. But, since it happened gradually, the concerns were not so obvious.
The key ingredient of ZDDPlus™ is ZDDP, which has been known to shorten catalytic converter life. Manufacturers have been redesigning engines for the last decade to minimize the need for ZDDP, in order to lower emission levels. One method is switching over to roller rockers.
Diesel engine requirements are much different that those of gasoline engines. The higher speeds and lower bearing surface-to-power ratios of gasoline engines require oil with higher shear ratings than most diesel oils. Diesels also have higher bearing clearances and that calls for higher viscosity oils. The additional detergents required for soot control actually reduce the effectiveness of added levels of ZDDP found in diesel oils. Also, newer diesel oils beginning in 2007 have greatly reduced their content of ZDDP.
Historically, EOS was the most concentrated ZDDP supplement available. It was intended to boost ZDDP levels of oils that already contained EP additives. EOS was packaged in a 16 oz bottle. It also sold for over $10 per bottle. ZDDPlus™ is packaged in a 4 oz bottle and contains TWICE the amount of ZDDP contained in EOS, since it is intended to be used with newer oils that contain little or no ZDDP. In the summer of 2007, EOS was discontinued, making it difficult to find today.
Some of the “Break-in” or “assembly lubes” offered by cam manufacturers contain marginal amounts of ZDDP while others offer virtually none. In most cases these products are intended for initial run-in and rely primarily on other additives such as MDS (molybdenum disulfide). These products are seldom recommended for continued use and most are intended to be removed before the engines are put into service.
Automotive engines have always been designed and warranted to work properly with the current available oil at the time of manufacture. There has not been a single off-the-shelf additive shown to perform any beneficial function except financial gain to the additive seller. Unlike other additives that have never been recommended by manufacturers, ZDDPlus™ is a replacement for the long-used component of oil that manufacturers once required, but over the years have been forced to remove from the oil for the benefit of newer cars at the expense of older cars.
The performance record of ZDDP is well established. We make virtually no claims for ZDDPlus™ , EXCEPT that it restores the EP (extreme pressure) function of the oil to the level originally required for your older car. Other additives make claims so ludicrous; they cannot be accepted based on common sense. If the claims attributed to most additives were even partially true they would have been part of the standard crankcase fill directly from the manufacturers like ZDDP has been for decades.
A quick search of Yahoo or Google will immediately provide one with numerous sites that deal with this subject. Most sites are credible although many date back several years to a time when things were not as critical as they are now in 2008.

Why ZPlus?

ZDDPlus™ is an oil supplement that contains very high concentrations of the well-known additive ZDDP (Zinc Dialkyl Dithiophosphate), which has been the primary EP (extreme pressure) ingredient in all quality motor oils for over 70 years. However, beginning in the late 1980s, the concentration has been greatly reduced as newer oil classifications have come on the market.


Hear From Our Customers

We use ZPlus on all of our Flat Tappet built motors.

Ron Hutter , Hutter Race Engines

ZDDPlus is the best insurance to protect your classic or high-performance flat-tappet engine!

“Big Daddy” Don Garlits, NHRA’s #1 Drag Racer of All Time