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Zinc in motor oil

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#1 Barney Eaton

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Posted 18 October 2012 - 01:46 PM

I get Hemmings but don't remember seeing this article on zinc in motor oil for old cars .......... click the link to read

Tech 101: Zinc in oil and its effects on older engines | Hemmings Blog: Classic and collectible cars and parts
Barney Eaton
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#2 Dave@Moon


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Posted 19 October 2012 - 04:42 AM

Most engine and engine component manufacturers recommend zinc and phosphorus content of more than 1,200 PPM for break-in; in fact, many will void warranties on camshafts or crate engines if this minimum is not found in the oil sample you supply when returning broken parts for warranty."

Even the author of the article appears to ignore that little tidbit for the rest of his writing. It's not surprising that most readers fail to notice.

"As the new API rating SN becomes available in the next year, even more caution should be taken as the levels will be reduced even further."

This I have no explanation for. The SN standard was put in effect over 2 years ago beginning with the 2011 model year cars, and did not change from the SM standard of (effectively) 800 ppm ZDDP. How that statement comes out in an "expert" writing released last week is beyond me.

....if you are purchasing off-the-shelf oil for your classic car, ILSAC multi-viscosity oils rated SM or CJ-4 should have stated zinc and phosphorus additive supplements for use in older engines or an additional separate additive should be purchased and used with the new oil.

Debatable at best.


Bob Olree, Chief and Senior Engineer for GM Powertrain Fuels and Lubricants Group, reviewed and contributed to the SM standards (that originally reduced ZDDP to current levels) professionally for General Motors. He personally did the backwards compatibility testing on older engines for the current motor oils on the market. He restores antique cars himself. And he wrote this: http://www.nonlintec...e/oil_myths.pdf

The argument put forth is that while these oils work perfectly well in modern, gasoline engines
equipped with roller camshafts, they will cause catastrophic wear in older engines equipped
with flat-tappet camshafts.

The facts say otherwise.

Backward compatability was of great importance when the Starburst oil standards were
developed by a group of experts from the OEMs, oil companies, and oil additive companies.
In addition, multiple oil and additive companies ran no-harm tests on older engines with the
new oils; and no problems were uncovered.

The new Starburst specification contains two valve-train wear tests. All Starburst oil
formulations must pass these two tests.
1 Sequence IVA tests for camshaft scuffing and wear using a single overhead camshaft
engine with slider finger (not roller) followers.
2 Sequence IIIG evaluates cam and lifter wear using a V6 engine with a flat-tappet system,
similar to those used in the 1980s.

Those who hold onto the myth are ignoring the fact that the new Starburst oils contain about
the same percentage of ZDP as the oils that solved the camshaft scuffing and wear issues back
in the 1950s.*
(True, they do contain less ZDP than the oils that solved the oil thickening issues
in the 1960s, but that's because they now contain high levels of ashless antioxidants not
commercially available in the 1960s.)

Despite the pains taken in developing special flat-tappet camshaft wear tests that these new
oils must pass and the fact that the ZDP level of these new oils is comparable to the level found
necessary to protect flat-tappet camshafts in the past, there will still be those who want to
believe the myth that new oils will wear out older engines.

Like other myths before it, history teaches us that it will probably take 60 or 70 years for this
one to die also.


*By way of explanation, from 1965 through 1971 the then current API Standard for motor oil was the SC standard. SC motor oils contained up to 800 ppm ZDDP, exactly the same standard as SN oils today. It was later increased to 1000 ppm under the SD (1971-1979) standard, attaining the (frequently eulogized) peak levels of ZDDP only in the 1980s and early 1990s..

Edited by Dave@Moon, 19 October 2012 - 04:46 AM.
added "(to current levels)"

"The saddest aspect of life right now is that science gathers knowledge faster than society gathers wisdom."--Issac Asimov

"Whisper words of wisdom"--Paul McCartney

#3 D Yaros

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Posted 19 October 2012 - 09:46 PM

Interesting info, to be sure! Myths/wive's tales do have a persistence factor. I guess what may be said is that ZDDP levels of between 801-1,200 PPM won't hurt when used in pre '80 vehicles?

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#4 old-tank


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Posted 20 October 2012 - 12:44 AM

Interesting info, to be sure! Myths/wive's tales do have a persistence factor. I guess what may be said is that ZDDP levels of between 801-1,200 PPM won't hurt when used in pre '80 vehicles?

Bingo, give the man a prize --->freedom to tear around the country in his old iron without worrying about the oil!
When I rebuilt my nailhead (55) 80,000 miles ago I smeared the cam and lifters with the appropriate lube, added GM EOS and then used Castrol 20w-50 since, changing once a year (3,000-8,000 miles) ---no oil related issues.
Most of the reports of cam wear are in performance engine with heavier valve springs...
1970 repairs

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#5 NTX5467


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Posted 20 October 2012 - 01:54 AM

I have a copy of the GM Engineering paper which has the "valve tappet weight loss from wear" information in it. This was for the validation of the "SM" oil standard. I also have a copy of the instruction sheet for a Chevy flat tappet 427 crate motor. Oil recomendation is "SM" for it. This was when "SM" oils had been out for a while.

Adding the "break-in" wording to the situation has been mentioned before, but not with respect to a particular zddp level. It is interesting that the 800ppm zddp was the amount which fixed the scuffing issues "back then".

Old-Tank's comment about "normal" valve springs is appropriate, PLUS relatively "easy" cam lobe profiles, which don't need heavy springs for the engines to turn higher rpms reliably. At least for the stock-spec engines of the 1950s and earlier 1960s. What made those cams so allegedly "radical" back then was the fact they were in approx 300 cid engines, not the higher lifts and longer durations which began appearing in the middle 1960s and 400+ cid engines "for sanctioned racing use", as NHRA, AHRA, and NASCAR.

In those earlier times, if you didn't change the oil at around 3000 mile intervals, engine life tended to suffer. Then Ford started their 6000 oil change interval in 1963, which changed everything . . . but there were also some upgrades in their OEM oil fiter "guts", chassis lube and wheel bearing lube with "moly" in their grease specs, and some upgraded motor oil specs that year. The early 1960s was the beginning of lots of automotive equipment improvements and upgrades which then tended to peak in the middle 1960s . . . except for motor oil which kept on getting better each year. More viscosity improvement chemistry which brought us the "super oils" of 10W-50 and such in approx 1970 and later. Castrol GTX had "liquid tungsten" for their special additive back then. NOT to forget the huge number of motor oil "improver" additives . . . including one called "STUD", which had a good amount of zddp in it. Not a lot of "shame" in buying normal oil and putting the special-purpose additives in it , back then, especially since everybody had the additives, but not everybody had the fancier motor oils in stock. And then there were the people who termed Castrol GTX as "motorcycle oil" and questioned its use is cars . . . not realizing that it had been used in cars which had run up and down the Autobahn for many years.

Thanks for the additional comments, Dave!


#6 54fins



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Posted 20 October 2012 - 02:52 PM

oil additives can be debated forever. The real bottom line is don't leave old oil in your car! Against my better judgment, I can't resist starting up an old car- just human nature. If you service all the fluids every year, odds are you won't have any trouble. I toss in the zinc additive, more from being a tech head than any real conclusive evidence it's needed. I also prefer 5w-20 in my buicks- not only because that's what the manual recommends but firsthand experience. Ever see the ad where they drain the oil out of an engine and run it? A little oil goes a long way. I do like to get all techie on these subjects but every smoked engine I've seen (and done) had old oil in it. Every seized nailhead sat for years, ran great but clunk- plugged oil passage. Also, old lifters and new lifters have different metallurgy. You either replace all of them and the cam or none of them. New and NOS don't mix. Most modern oils are so good that keeping it in the engine is more important than exactly what type. Buicks are low RPM motors- at least our old ones. A 1500 mile cam was probably rubbing the wrong lifters.
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#7 Bleach


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Posted 20 October 2012 - 04:45 PM

My understanding is that the zinc in diesel oils is more than adequate for use in flat tappet engines. The only drawback is those oils have high levels of detergents. Those detergents are formulated to keep the internals clean and that may dissolve any anti wear films on moving parts.
A low detergent diesel oil, if there is such a thing, would be the oil to use.


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#8 NTX5467


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Posted 20 October 2012 - 06:07 PM

"Anti-wear films"? News at 10pm?

Almost every one of the newer (and older) diesel motor oils also have ratings for gasoline engines in their credentials. I don't know that it's the detergency additives, as such, which result in cleaner innards of the motors, or if it's more of an ester-based formulation that does it (if it's possible to have an ester-based situation in non-synthetic motor oils). I haven't seen an increase in the phos and calcium levels (which are part of the additive packages, as I understand it) in the most recent diesel "dino" oil formulations, from the virgin oil analysis at www.bobistheoilguy.com . It has been stated on that website, when the issue of using add-in zddp additives, that too much zddp can nullify the effects of the additive package, somewhat. I believe the Gibbs' Racing Break-in motor oil has lots of zddp in it, as does their NASCAR oil, but we all know that those oils aren't really intended to be in a "consumer" engine for 7500 miles.

I do believe the new Liquid Titanium additive (in Castrol and Kendall GT motor oils) allows the zddp levels to be decreased a little, as the presence of "moly" might also. I'd term these as "anti-wear films", though, as each can penetrate the base metal's surface to result in less rubbing friction. Seems like the analysis' I've seen of the Chevron Delo400LE shows some moly in that motor oil, plus the dialogue on the bottle also tends to give the suspicion it's very similar to a blended synthetic, but never does make that statement per se.


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