Oil Discussion - Part II

[zodiacblue442]

Thought I'd pass along this information. I've heard this / read this in other places so there's probably something to it.

I read an article in my dad's NAOC (National Antique Oldsmobile Club) newsletter, Runabouts To Rockets, about a caution pertaining to the new motor oil API Service SM. It seems that in the past, motor oil had an additive in it called zinc diakl-dithiosphoisphate (ZDDP) which is necessary to prevent failed camshafts in earlier engines that use flat bottom lifters. Modern engines now use roller lifters and don't have the friction that the flat lifters do. It seems that the ZDDP tends to clog catalytic converters so there was motivation to remove the ZDDP from automotive motor oil. It says that synthetic motor oil also rated SM doesn't have ZDDP so it won't do your engine any good to use that either.

The article recommends using 15W40 CI-4 rated oil formulated for Diesel engines which still has the ZDDP additive. Just make sure you read the service rating on the bottle and it doesn't say SM. You can also add a half ounce of General Motors Engine Oil Supplement to each quart of SM oil, but the stuff is expensive.

There is also an extensive article on this subject in the August 30, 2007 issue of Old Cars Weekly.

As well as the CI-4 rated diesel engine oil, I know that most oil considered "racing oil" has an API Service rating of SJ. It wll still have the ZDDP in it. I use Brad Penn Grade 1 10W-30 racing oil in my race car and my 442. There's plenty of other good brands of racing oil out there too.

I would think the rapid camshaft wear would be a concern for any engine with flat bottom lifters - lawn and garden equipment, generators, boat engines, etc. in addition to pre roller lifter car engines.

[damaged442]

ZDDP = zinc dialkyl dithio phosphate

Sorry bud, that's what I get for being a chemistry dork. ;) :D

[zodiacblue442]

Thanks, Bert! I knew I'd screw that up. It's all alphabet soup to me! :p


ZDDP = zinc dialkyl dithio phosphate

Sorry bud, that's what I get for being a chemistry dork. ;) :D

[texxas8902]

Cams have been eaten by lifters and sent metal throughout the engine in 3 instances that I know of in the last year and a half or so. One was a fresh professional race shop built Buick 455 engine built to stage 1 specs in a 73 Buick GS. Crane cam went flat, ate a lifter, metal shavings throughout. The guy spent another $3500 at a different race shop.
The other 2 were Chevy small blocks built all radical and crazy by a neighborhood 19 year old, orders the most extreme of everything, the last one on the bottom of the list, most lift, biggest carb, highest stall. I'm sure you all know one of these guys, thinks bigger is better for everything. Wouldn't listen when I tried to tell him to use Shell Rotella diesel oil in his motor after he lunched it the first time with a Summit cheapy super high lift solid cam with a noisy gear drive on a Chevy small block 305 with dual valve springs for the stupid lift cam. This kid thinks he knows it all. Without the zinc in the oil it made metal cam and lifter shavings in record time. When he did it again I laughed at him. He is a friend's son and is a decent mechanic for his age but is as dumb as cat shit when it comes to listening to people who just might know something. Of course he knows it all so he doesn't have to listen.
The rotella is available at most parts stores and has the zinc. I have been using it for a couple of years now in cars that need the zinc and amazingly no problems.
I have used Lucas oil treatment in the past with good results but I don't know if it has the zinc additive. Does anyone know if any of the oil treatments besides the GM additive have the zinc?

[damaged442]

ZDDP is synthesized when phosphorus pentasulfide is added to different types of alcohols, n-butanol and 2-ethyl hexanol I believe. Zinc oxide is added to this and you get your ZDDP. It is susceptible to oxidation and degradation with exposure to high temps and presense of moisture. There are quite a few byproducts formed with the decomposition of zddp, but eventually you have zinc and phosphate. The numerous byproducts formed aren't friendly with the catalyst in your converters and :eek: ! There were a bunch of articles I wanted to check out on the topic, but most chemistry journals are by subscription only and I don't have access to them at home. I'll nose around work tomorrow and see if I can dig up anything worthwhile and more specific on it.