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Zinc vs. ZDDP - are they the same thing?


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Yes.  The Z is for zinc, the P is for Phosphate.  It's much easier that saying  zinc dialkyldithiophosphates.  😎  Zinc is not as prevalent in oil as it once was because tolerances along with overhead cams, etc. have reduced the wear factor in modern engines so larger quantities of zinc are not necessary.  Mobil synthetic 1 in certain viscosities has at a minimum of 1,000 ppm.  Plus you can buy it at Wally World for around $25 for a 5 quart jug.  No need to go super exotic just to get the Z and P that your flat tappet engine requires. 


Edited by RivNut (see edit history)
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There are issues with "too much " zddp" in the oil.  What's too much?  Probably the 3000ppm in some of the Joe Gibbs racing oils, as an example.  Too much zddp can compromise the other parts of the additive package related to detergency, from what I've read.  Everything must be in balance for the best results.


How do the "racing oils" get by with the 3000ppm level?  They're only in the engine for about 500 miles, then they are changed.  No real detergency issues with that low mileage on the oil, I suspect.


About 5 years ago, most of the diesel-rated oils (i.e., Shell Rotella T 15W-40 "dino") had right at 1500ppm zddp.  Later versions of that oil are now closer to 1200ppm zddp, in synthetic or "dino".  The Amsoil "Z-Rod" oil is about 1500ppm zddp, as I recall.


Other than the PQIA, also check www.bobistheoilguy.com Virgin Oil Forum postings of oil analysis done by individuals.  Most of the tests are privately-funded by the posters and are performed by Blackstone.


On ANY oil analysis results, always check the date the analysis was done.  VERY important as it can change year-to-year, by observation.


Below are a few of the Virgin Oil Analysis postings from the www.bobistheoilguy.com website.  There are about 50+ pages of such, not all with postings, though.  You can also find a chart of Mobil 1 motor oil composition on the ExxonMobil website  Most all of the "consumer" oils have zddp levels of about 1000ppm, as the "car" oils are usually in the 700-800ppm zddp level range.


API rating "SL" was the last oil that was supposed to have 1000ppm zddp in it.  The later "SM" oils went down to about 800ppm and lower.  The original "SN" oils were in the 700ppm range, but as the "SN Plus" oils are attuned to the GasDirectInjector motors currently in use, their additive packages have been tweaked a bit from the orig.  "SN" oils.  ONE change was to increase the zddp levels back to 800ppm, as Calcium was markedly reduced.  The "S_" designations are for "Spark Ignition" engines, as the "C_" designations are for "Compression Fire" (diesel) engines.


Other than the noted Rislone zddp product, almost every camshaft vendor now has some sort of zddp oil additive for sale.  Financially better to find an oil with at least 1000ppm zddp to start with.  AND one that is readily-available at common places.  To me, that means the "diesel-spec" oils, with the basic "C_" designations on them, BUT also with a secondary gas engine rating.  BUT the way some things seem to be changing, be sure to check the oil analysis websites every so often to make sure what's what.




OIL__MOBIL 1_0W30_RACING_NEW FORM_2011_Blackstone-E41615.jpg

OIL__ROTELLA T6_5W40_CK4_Q24Vvst.jpg


OIL__VALVOLINE_PREM BLUE_10W30_CK-4_full-78067-26201-c73e9925_7f3a_44f7_95c9_752b0414b11f.jpg

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Search "zinc" on this forum for much past discussion.

 Unless you have a high lift cam with heavier than stock valve springs, you don't need any added zinc.

Oils today have more zinc than when these cars were new...zinc level was increased in the "muscle car era".

There will always be those that caress each bottle of oil or additive while mumbling ritual incantations while it flows into the engine :D.

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On 10/18/2019 at 5:48 PM, RivNut said:

because tolerances along with overhead cams, etc. have reduced the wear factor in modern engines so larger quantities of zinc are not necessary. 


My understanding is that ZPPD was reduced because of it's negative effect on catalytic converters.  

Edited by Robert G. Smits
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That is a true statement. But the ZDDP is not necessary in modern engines where there's not as much friction and the lubricants are better today than in the years of flat tappet cams and other parts that were prone to metal on metal wear. The lowered zinc levels were two-fold.  

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There are other additives that will do the same thing as zddp does, just that it was the least expensive way to do it.  Remember, too, that oil change intervals were much less back when the '50s-'60s cars were new, so the zddp reserves got replenished more often than after Ford came out with their 6000 mile factory-recommended oil changes in 1963.


Even with the change to roller cam followers, there are still other friction areas in the motor, other than the bearings.  Rocker arm ends, for one (the non-rollerized versions), phshrod ends (where applicable), timing chain tensioners (even the "guides"), etc.  


Additionally, the oil base stocks are probably much better now than when the older cars were new cars.  Not related to the brand of oil or where it came out of the ground.  Remember the "Pennsylvania Crude" long-chain hydrocarbons?).  When the whole cam lobe wear issue arose, Comp Cams first recommended using "Either Shell Rotella T or synthetic motor oil".  At the time, Shell Rotella T (diesel as the main spec application, gas motors as the secondary application) probably had something like 1400ppm or zddp in it.  Current verions are more like 1200ppm, from the oil analysis reports posted to the BobIsTheOilGuy website.  Reduced a bit, but NOT entirely diminished as some seem to believe.  The Mobil 1 Turbo and Diesel Truck oil is 1000ppm, by their admission in their oil spec charts.


European manufacturers each issue their own "approvals" for motor oils used in their respective engines.  Some of the VW diesel cars used a synthetic oil with 1000ppm zddp in it.  Seems they ran the high pressure fuel injection pump off of one lobe on the camshaft.  Not enough zddp would flatten it over time.  Other than the particular VW approval number, SL synthetic oil was the USA-type spec.


Zddp isn't the only part of the oil additive package whose level can affect catalytic converter/emissions hardware longevity.  Lead in gasoline would render the catalyst ineffective over time, but could regenerate itself if unleaded fuel was used afterward.  In a time when zddp levels were still "higher than what we have today".  BUT as everything gets downsized when possible, catalytic converters are no different, by observation.


Used to be that all factory ultra high-perf engines spec'd Mobil 1.  Then, suddenly Chrysler started to spec a particular "SRT" oil from Pennzoil.  Others have defected from Mobil 1 to Pennzoil.  BMW defected from Castrol to Pennzoil (Royal Dutch Shell) a few years ago.  Probably had something other than cost as a motivator, I suspect?  When looking at the postings of oil analysis tests, there were a few "metallic additives" which were significantly less in the Pennzoil SRT oil, compared to Mobil 1, which both could affect catalyst longevity.  Remember that "catalyst longevity" will relate to the emissions warranty costs of the vehicle, as it ages.  I suspect this is why the Penz SRT oil is what it is and many Chrysler dealers stock in in bottles rather than bulk.


Unbeknownst to us in the USA, Japan and Europe had their own oil performance specs.  Generally, the Euro "GF" or "ILSAC" specs relate to emissions hardware longevity.  The Oriental "JASO" specs relate to other areas, as I recall.  There is a particular GF spec which relates to the decrease I zddp, just as the API "SL" spec was 1000ppm zddp.


One interesting thing I discovered in search for riding lawn mower oil.  The Briggs & Stratton 10W-30 full synthetic oil is sold in "ounces" bottles.  The Rotella T5 sy-bled oil (noted above) has a very similar additive package, but is sold in quarts and gallons at less unit cost.


REMEMBER that due to crankcase condensation, it's BEST to drive the car for about 20+ miles at a time, especially I cooler/cold weather.  That's the reason for the "Trips less tha 10 miles" commet in owners manuals over the years, for more frequent oil changer.  I'm recommending doubling that to 20+ miles to ensure that the automatic transmission lube gets similarly hot enough to cook out ay condensate in the mechanism.  The engine temp gauge only shows coolant temperature, NOT how hot the crankcase or ATF might be.




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