How much ZDDP gets used up?

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I have always heard that some ZDDP gets used up during the life of the oil. Say if a car requires a 10,000 oil change interval, and the oil has 1900 ppm of zinc when fresh, about how much zinc will it have at the end of 10,000 miles?
 
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Blink7. I don't think there is that much of a reduction. Zinc levels average around 800/850 ppm in SM oil. If you go to the UOA section you will see the levels seem to be the same or close to the VOA.
 
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The answer is, it depends on the engine, also oil technology/design it much better today and Zinc/ZDDP is not the only additive that has anti-wear properties. In older engines with flat-tappet cams and more metal-on-metal contacting parts there will be a chance for increased wear and thus the oil's additive package provides a protective barrier but it also used up in the process. So IMO today's oils offer better protection than yesterday's oils with more ZDDP/Zinc etc. but they just can't be used as long in most cases in older engines. This whole "I have to add ZDDP to my oil because of flat tappet cams" is nonsense IMO, you just need to shorten your OCI IMO.
 
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 Originally Posted By: StevieC
. . . This whole "I have to add ZDDP to my oil because of flat tappet cams" is nonsense IMO, you just need to shorten your OCI IMO.
If the emphasis is on the "have to" part (as in there's no other way), I agree. On the other hand, so long as it's done sensibly, and with an understanding that you're making yourself a test case, adding some ZDDP may be a way to get back the protection for old engines, without having to resort to short OCIs.
 
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AFter break in , extra zinc is not needed. Maybe with a super duper hot cam and springs. But according to an oil engineer on a car talk show I was watching, the whole deal is not a real issue.
 

Blink7

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Well I do think its an issue, and a real one. I just had my cam ruined with these newer oils. And to top it off, the oils I have ALWAYS used in the motor have been synthetic 5w-40.
 Originally Posted By: mechtech2
But according to an oil engineer on a car talk show I was watching, the whole deal is not a real issue.
 
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Well, Blink7, make a liar out of me and tell me this was a totally stock cam with mild spring rates. ..or was this power plant by Jeg's Plus (Jeg's not being good enough).
 

Blink7

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It was totally stock everything with hydraulic lifters. An inspection of the cam and lifters was done 4 years ago at 60,000 miles, and everything looked brand new. Another inspection was done a couple of weeks ago at 140,000 miles and the cam is ruined along with atleast 4 lifters. I should also note that the oils used between 60k and 140 k have been Mobil TDT 5w-40 and Rotella synthetic 5w-40.
 
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That's a surprise. What is this, btw? You mentioned 10k intervals ..that spells Honda to me (still looking in tea cup wondering where the reading of the tea leaves went wrong). Those two oils would be the last thing I'd suspect.
 
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 Originally Posted By: Blink7
Its a 2000 VW Jetta TDI.
That is surprising. Please post your experience with your TDI and oils used in the Heavy Duty Diesel Oil forum. I am almost sure a lively discussion will occur since the oils you used are widely popular. My MB OM602 has flat tappets too.
 
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You have another problem. The oils you used had the highest Zinc/Phosphorous of nearly any 'off-the-shelf' oil you could have used. That was not your problem. You about had me worried.
 
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I thought Zinc sacrificed itself during the anti wear process ? The above mentioned a good point at the UOA of the oil the Zinc is still high ! but we push for more zinc in the oil. Does the effectiveness of the Zinc diminish over time ??
 
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 Originally Posted By: Blink7
It was totally stock everything with hydraulic lifters. An inspection of the cam and lifters was done 4 years ago at 60,000 miles, and everything looked brand new. Another inspection was done a couple of weeks ago at 140,000 miles and the cam is ruined along with atleast 4 lifters. I should also note that the oils used between 60k and 140 k have been Mobil TDT 5w-40 and Rotella synthetic 5w-40.
Have you looked at the VOAs and UOAs for RTS and TDT? Both have >1100PPM of Zn/P, and that's even in the SM rated version of RTS. That should be PLENTY for any stock cam, which is why I use RTS in my old muscle cars and my Jeep. I'm going to go out on a limb and say that I *seriously* doubt the oil ruined the cam. I think you've got something else going on in there.
 
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RE the original question of how much of the ZDDP gets used up... I found this thread on the UOA page http://bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1550996&fpart=1 As you can see, after a 14-hour race the Zn/P levels dropped from 1444/1252 PPM in the VOA, to 1198/1094 in the UOA. It was beaten on pretty hard from the sound of things. If you read the whole thread, there are some other things that bring the analysis into question (fuel dilution, significant change in the Mg and Ca levels, etc.). But its a "FWIW." Keep in mind that ZDDP *only* gets used up under specific conditions, so how fast it gets used depends very much on how the engine is operated and what kind of internal design features the engine has (valve spring pressures and ramp rates on a flat-tappet cam being one key factor.)
 
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 Originally Posted By: OVERK1LL
Perhaps a defective camshaft.
Been there, done that years before there was any such thing as SM oil. But then my flawed cam didn't last anywhere close to 60k miles, either. More like 5k before a lobe wiped. Cams and lifters are tricky bastages. The surface hardening is key to how long they last, and they will fail *super* quick after the hardening layer is breached. It may take 400k miles to breach the hardening or only 1k, but the time from breach to failure will be measured in hundreds of miles in either case.
 

OVERKILL

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 Originally Posted By: 440Magnum
 Originally Posted By: OVERK1LL
Perhaps a defective camshaft.
Been there, done that years before there was any such thing as SM oil. But then my flawed cam didn't last anywhere close to 60k miles, either. More like 5k before a lobe wiped. Cams and lifters are tricky bastages. The surface hardening is key to how long they last, and they will fail *super* quick after the hardening layer is breached. It may take 400k miles to breach the hardening or only 1k, but the time from breach to failure will be measured in hundreds of miles in either case.
Just another reason I am thankful to be running a billet roller in my performance junk.
 
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