Confused about zinc

[jeryst]

I have been reading letters in TW about the lack of zinc (ZDDP?) in new motor oils. I have also seen people trying to figure out which oils are best because of this. In several places, I have seen that STP contains a proper amount.

So I am a little confused about all of the discussion. Isn't the simplest thing to do, is just throw a can of STP into the crankcase at every oil change, and just not worry about it any more?

[Skip Lackie]

The issue of zinc and what's the best motor oil for old cars has been exhaustively discussed here. Rather than rehash it all again, try entering "ZDDP" or "flat tappets" in the search function of both this and the technical talk forum. A good summary is in the thread entitled "SJ oil" over on the technical talk forum.

No one knows how much ZDDP is in STP, because STP won't say. There are now motor oils on the market that are specifically formulated for older engines with flat tappets. There now are also additives with known amounts of ZDDP that can be added to any brand of motor oil.



Skip Lackie
Washington DC

[Gunslinger]

I've read a lot of different articles on the ZDDP controversy and none seem to totally agree on the issue. There does seem to be some constants...several years back there were substandard lifters and camshaft blanks being imported from offshore that were part of the problem. Also many of the issues related to lack of sufficient ZDDP in flat tappet engines were in high performance engines with high valve spring pressures.

Basically, if a camshaft is going to fail due to lack of ZDDP, it will be far more likely to occur during break-in. After that its chances of doing so fall dramatically. After all, there's still millions of flat tappet engines out there motoring on with no problems at all with modern oils.

There is some indications that adding too much ZDDP can increase long term wear while decreasing short term break-in issues. It all depends on which article you read. You can't just add ZDDP without knowing the proportions needed.

You can certainly add a container of STP and be OK. You can go to a GM dealer and get a container of EOS (Engine Oil Supplement). From what the parts manager at a local GM dealer told me, it's nothing but GM's version of STP (if you can believe what a parts guy says). Regardless, it's more expensive than STP and does the same job.

You can buy one of the diesel rated oils that have higher levels of ZDDP, like Shell Rotella, but even that is being reformulated with lower ZDDP levels. There are other brands like Brad Penn and Joe Gibbs oil that are formulated with the old levels of ZDDP.

You can do any of these things, but as you said...the simplest thing is add a container of STP. The real secret is regular oil and filter changes and a regimen of preventive maintenance.





Poet...Mystic...Soldier of Fortune. As always...self-absorbed, adversarial, cocky and in general a malcontent.

[okc63avanti]

Valvoline VR-1 Racing Motor Oil has the proper amounts of zinc and phosphorus in the oil. Here's a link to there product page with detailed info on oil specifications.

http://www.valvoline.com/pdf/VR-1_Racing_Motor_Oil.pdf

<div align="left">John</div id="left">

<div align="left">'63 Avanti, R1, Auto, AC, PW (unrestored)</div id="left">

[Supercharged57]

Ive been up on this subject for a few years now.

Chevron Dello 400 LE 15-40 and Valoline VR-1 Racing has correct amounts of zinc and some Shell Rotella -T.

To avoid and cam failure issues I now use a bottle of Comp Cams brand cam & lifter break in oil in evey oil change to avoid a any loss.

This can also be added to oils that contain no zinc but it's better to have it than not.