ZDDP - WHAT IS IT?
Do you know what zinc dialkyldithiophosphate (ZDDP) is? You should, if you are a WWII vehicle owner! It is an effective lubricant preventing cam and lifter wear. Our old engines have flat tappets which bear against the cam lobes. Modern engines use roller cam technology so there’s not the worry about tappet to cam wear.
Classic car owners have been concerned about the reduced levels of ZDDP since 2004, when concerns about this compound harming the catalytic converters arose. The oil manufacturers reduced the ZDDP concentration in the motor oils to 800 parts per million (PPM). This is NOT a high enough concentration of ZDDP to prevent wear in our old engines!
According to the SAE Tech Bulletin # 770087, operation of a flat tappet engine without adequate EP additives such as ZDDP quickly leads to lifter foot scuffing and cam lobe wear. Camshafts are typically only surface hardened leaving the core ductile for strength. According to the SAE Bulletin, once cam lobe wear reaches 0.0002, "subsequent wear is usually rapid and catastrophic." Two ten-thousandths of an inch is one fifth the thickness of an average human hair. In order to make engines last in the absence of ZDDP, virtually all IC (internal combustion) engines designed in the last ten years utilize roller lifters. Today, ZDDP has been removed from practically all automotive engine oils, rendering them unsuitable for use with older engines with non-roller lifters.
API oils have always been more than adequate for the engines designed when the oil was current. The use of current API grade oils has always been adequate to satisfy car manufacturer's requirements and warranty demands. Historically, with few exceptions, newer API grades have superseded the performance of their predecessors. The removal of ZDDP has resulted in a clear change to that philosophy. It has never been necessary or desirable to include additives or supplements to any API rated oil to meet car manufacturer's specifications or warranty requirements. In virtually all cases, off-the-shelf additives amount to little more than automotive snake oil. Current additive technology has yet to develop an EP anti-wear agent as effective as ZDDP. Consequently, if these additives actually had adequate levels of ZDDP, they would be incompatible with modern engines and void manufacturer's warranties.
For a full discussion of ZDDP I would suggest you go to the web page http://www.zddplus.com/ and read the comments and suggestions there.This is from “Macy’s Garage”:
Motor oil is one of those HOT buttons that is always capable of starting a debate among car guys. Most gear heads have a particular brand of oil that they feel is the best, and will debate the merits at length with anyone who doesn’t concur with their opinion. But this latest debate among vintage car folks over ZDDP is widespread and touches everyone addicted to motors designed more than 20 years ago. You see, for most of the last century, the almost universal method to open and close engine valves was via flat tappets (solid or hydraulic lifters if you will), and the ZDDP additive was there to prevent or reduce wear between the lifters and the camshaft (#6 and #7 respectively in the diagram to the right). But ZDDP in the minute amounts of oil that will get burned and exit through the exhaust system will shorten the life of catalytic converters. Thus the EPA mandate to eliminate ZDDP from engine oil, and the auto makers have responded by designing engines that utilize roller lifters or overhead camshafts, and have no need for the protection offered by ZDDP.
Motor oil has carried a performance rating from the American Petroleum Institute (API) since the days of horseless carriages. Pick up any quality motor oil at your local auto parts store, and you’ll see the API logo on the bottle. (I grew up with oil cans, and I’m still having trouble getting used to this oil ‘bottle’ thing!) Automobile oils have a two letter service designation, which always begins with the letter “S”, and then works its way down the alphabet for the second letter. Historically, the newest designations have always met the performance specifications of the previous ones, and so there was never an issue with using the latest technology motor oil in vintage autos, until now. While ZDDP levels have been gradually reduced starting with SG oils in 1988, it is the latest SM designated oil with the nearly total elimination of ZDDP has raised the concerns of all vintage auto enthusiasts who fear the worst for their cams and lifters.
The API designations do not necessarily tell the whole story on the ZDDP content of the oil. Some SM oils will still contain some ZDDP, and some of the earlier designations may not contain enough to protect our early design engines. So the bottom line is that you should use the API ratings as a starting point in your search, and then if the oil bottle does not specifically mention ZDDP and the protection it provides for camshafts and lifters, place a call to the tech line shown on most bottles and confirm that you are getting what you think you are!
Here is a response from Castrol regarding their products and ZDDP:
Castrol does offer the following products that contain Zinc at a level that is higher than the Zinc level found in oils (API SG) marketed during the "muscle car" era of time:
* Castrol GTX 20W-50 (SL, SM)* Castrol GTX Diesel 15W-40 (CI4, CH4, CG4, CF4, CF, SL)* Castrol GTX High Mileage 20W-50 (SL, SM)* Castrol HD 30 (SL, SM)* Castrol HD 40 (SL, SM)* Castrol Syntec Blend Truck 15W-40 (CI4, CH4, CG4, CF4, CF, SL) (Semi-synthetic)* Castrol Section Extra 15W-40 (CI4Plus, CI4, CH4, CG4, CF4, SL)* Castrol Hyperons S 15W-40 (CI4Plus, CH4, CG4, SL) (Semi-synthetic)Thank you again for your continuing patronage,Castrol Consumer Relations(ARTICLE COMPILED BY THE WEBMASTER)
