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About six months ago I read about the reduction of zinc dithiophosphate (ZDDP) in engine lubricating oils supplied with American Petroleum Institute (API) approval that could affect sliding and high pressure friction surfaces in our cars. API-certified oils of 30W and lower are now required by the EPA to have reduced levels of the zinc compounds needed in older engines. Additives such as zinc, manganese and/or phosphates have been reduced or eliminated in certain new engine oils. These additives can reduce the effectiveness of and eventually damage catalytic converters and introduce minute amounts of pollutants into the atmosphere. 

American Enginer Rebuildes Association (AERA) Bulletin # TB2333 directly addresses this problem. Major cam shaft suppliers and engine rebuilders have been aware of this effect for about a year. Crane Cams recommends certain break-in additives to prevent camshaft and lifter failure on newly rebuilt older engines. They suggest using diesel-rated engine oil on flat tappet engines. Castrol advises the use of certain non-API-approved oils such as diesel-rated oils or four-cycle motorcycle oils. 

Be aware that ìnew and approvedî engine oils may not be suitable for our aging MBs. Most rebuilders of British sports car engines are very much aware of this effect and have switched to using oils formulated to older API specifications. 

So what should the owner of an older MB use in his car? Mercedes-Benz produced a new publication in September 2006 ìFactory Approved Service Productsî (Order No. S-0473-07C from MBUSA at 900-367-6372 or request a .pdf copy from Technical Director George Murphy at [email protected]). This 26-page guide contains not only engine lubricating oil specifications, but also specifications for almost every car care product you may use on your Mercedes-Benz. For example, there are specifications for windshield washer fluid, door lock lubricants, paint care products, even fuels (diesel and gasoline) and fuel additives. Of course, most of the products are MB branded but other products are also named as approved. 

Reprinted with permission from George Murphy 

The Technical Director for the Club is available to assist members with their technical questions. He is furnished with technical manuals and bulletins from MBNA. If he is unable to answer a specific question from a member, he will request assistance from the technical staff of MBNA. Members only, please contact George Murhpy, (865) 482-9175, email [email protected]