The Stovebolt Site Forums The Shop Area Engine Shop More ZDDP info

I know this has been discussed to death on the forums here but I
just got off the phone with a Castrol engineer who said they no longer recommend ANY SM-rated dino product in a flat-tappet engine. As they continue to reformulate to appease the auto industry, (read, extend catalytic converter life) the zync content continues to decrease. The only thing they recommend for older engines now is their synthetics.

A couple of years ago the GTX series Castrol products still contained quite a lot of zync compaired to other brands and I've been a Castrol user for years but I'm getting a little worried about this now. I'm thinking It's time to switch to Shell Rotella or Mobile Delo. (A recent Hot Rod magazine article also recommends switching to diesel oils for flat-tappet engines).

The latest Diesel oils such as DELO and Rotella don't have the zinc required for flat tappets. Their purpose is to keep Diesel soot in suspension and to meet emissions standards. I prefer a motor oil that was designed for gasoline engines and them adding this http://www.zddplus.com/

There is still plenty of SL oils on the shelf where I live.
Doug

Royal Purple is SL rated. I'm wating for a response fom Valvoline concerning their synthetics, namely the Roush line that just came out.

Can SB oil be used in a Stovebolt?

I'm not an expert but I don't see why not. It would have the Zinc in it. I've been having luck buying the house brand oil at the local farm store. Their oil still has the SL rating.

Get the ZDDP additive and put it in with 5 qts. of any oil you want to use. You should be OK then with the flat tappets. That's what I've been using in all my old engines.

I've "heard" the STP red bottle has zink in it too. I wouldn't be afraid to run Rotella either. Amsoil oils are good and look for CJ-4 listed on the oil.

In the past GM always said to put a bottle of their EOS in a new or rebuilt motor. It was always recommended to not run it for an extended time period. Now, I understand the the new spec motor oils have reduced if no zinc at all present. I've also read that the zinc is only the "carrier" for the stuff that really coats the severe wear points such as the camshaft lobes / lifters. So, what is really needed on a motor that is well seasoned? Is it possible that to much additive could be put into a motor and cause the oil to be diluted?

Don

There's a lot of info on the zddplus site that crenwelge linked to. I know they're trying to sell you something but they document a lot of what they claim. They've tested engines with an overdose of ZDDP and the result is, no problems. I'm going to try a bottle with my next oil change along with my usual Castrol GTX 20-50. I have an account with Eastwood and they carry it so I've ordered a bottle and it's on it's way. $10 sounds like a cheap insurance policy to me. Oh, and they mention diesel oils and why they are unsuited for gas engines.

I wish one of the big oil co.s would formulate a blend to meet the needs of the tens of thousands of '89 and older engines still out there and still running but I suppose the sales numbers wouldn't support that.

ZDDP use one 4oz. bottle per 5 qts of oil.

I've seen ads in Old Cars Weekly for oil formulated for flat tappet cars. I've not bought any because I can still get SL oil at the farm store.

I look at bottles of oil whenever I go to the store. Many of the straight weights still have the SL rating. I have noticed that some of the marine and ATV oils still have the SJ rating. I guess since there is no emissions equipment on them, there is no need to worry about clogging up a cat. Something to remember also is that not all oils have zinc and some never did. Some have phosphated ash instead of zinc and it's been that way for years.

Just heard back from Roush, no plans for a straight 30 in the Roush/Valvoline line. However, the weights that are available are SL rated, so will be ok for the older engines.