We have become accustomed to every new specification for engine oil being superior to the one it replaced however that is no longer the case. The additive that protected our flat tappet engines ZDDP, has been removed from the most recent API oil specifications  and many of our collector car engines are are now in danger of camshaft and lifter failure.

Much has been written on the changes to engine oil and the effect it will have on our collector cars. I will give you my thoughts on the subject below but more importantly give you a compilation of articles on the subject.

The latest API oil specifications for passenger cars removed Zinc dialkldithiophosphate    (ZDDP) from the formula. *

ZDDP was the extreme pressure additive that protected flat tappets and camshafts from premature failure.

It was removed as it degraded catalytic converters.

As the manufacturers went to roller lifters over a decade ago there was no industry opposition.

Premature cam and lifter failures have shown up across North America ever since.

ZDDP was developed in the 1930's and used as a high pressure additive for gear and hydraulic oils. Some internet sources suggest GM wanted it added to motor oils to stop cam failures in their new 409 Chevrolet.

If we look at valve spring pressures from 1950 to 1960 we see them incrementally rise from a 40 lb. low on one engine up to 200 lbs. on the 409. Of course cam profiles and  rocker ratios will also play a part.

My thoughts are that if an engine was designed before 1960 it probably will have no problems with the new oils but it may be better to be safe than sorry. For later engines after that up to the last flat tappet engine in 1996 you should be very selective about break in oil and additives.

Personally I have no expertise in engine oils per se but have had a 40 year career in engine parts and automotive machine shop service. Presently I call on 40 machine shops in Saskatchewan, Manitoba. and N.W. Ontario and can attest that there are serious problems with the new oils when used in flat tappet engines. Stock 350 Chevrolet rebuilds are failing, mild street cam grinds that worked for years now fail prematurely.

While compiling the information below it was interesting to see Crane Cams do not recommend synthetic oil in engines stored for lengthy periods as is the case with most of our collector cars.

Although many of the articles below recommend a particular oil or additive it is a constantly changing landscape. Many of the diesel oils once recommended have changed for the worse as the new diesels trucks now have catalytic converters.

 Every manufacturer also has his own products to sell and you have to be vigilant about what you choose.  Racing oils do not have the additives for long term usage.  Additives  as shown below may be the only alternative.

Articles

AERA Bulletin TB2333      From the Automotive Engine Rebuilders Assn.  oil recommendations  (.pdf)

Comp Cams Bulletin 225  Covers break in and lubrication  (.pdf)

Oil is Killing Our Cars   by Keith Ansell an excellent article written in a play by play style

Joe Gibbs Racing Oil  One of many racing oils that contain high pressure additives

Crower Cams  A dated article on oils taken from the Crower cams website

Camcraft Cams An article by Charles Reichard on cams, oil, break in etc.

Bob Is The Oil Guy  Forums, information, charts  (link)

Crane Cams   Flat Tappet Cam Break-in Procedure, synthetic oil information. (.pdf)

Hot Rod Magazine (link) Check all 3 pages

Future Oils   A Penzoil article on GF5 specs..due 2009

Performance Oils and Additives  Engine Builder magazine

Richard Widman Corvair Oil  An excellent article covering a lot more than ZDDP

Additives

Oils

* The API-SM specification for Zinc content is .087% down from the .10 to .11 of previous specifications.