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ZDDP? and the use in older Z engines

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You are correct that 1000 ppm is .001%


Actually 1000 ppm is 0.1%

(1000/1000000)*100% = 0.1%

Somehow the previous quote kept bothering me, so I had to do the math to prove to myself that I wasn't crazy. (Well I may be crazy but I can do basic math)ROFL

Also, to quote this previously posted link:


"A higher level of ZDP was good for flat-tappet valve-train scuffing and wear, but it turned out that more was not better. Although break-in scuffing was reduced by using more phosphorus, longer-term wear increased when phosphorus rose above 0.14%. And, at about 0.20% phosphorus, the ZDP started attacking the grain boundaries in the iron, resulting in camshaft spalling."

I suspect that the study he mentioned explains why none of the oils listed on the Mobil-1 chart contain more than 1200 ppm phosphorus.

Everything that I read on this subject comes back to flat tappets. Actually this makes sense, because unlike the L6 motors where there is clearance between the cam and the rocker arm most of the time, on a flat tappet motor the lifter is in constant contact with the cam. This is particularly true in engines with hydraulic lifters. (read American V8s) If you read the thread discussion further, the people who contradict the "debunker" are talking about high lift OHV engines with high spring pressures. (Street rods etc.) Again, those are not an apples to apples comparison to the valve geometry of most OHC engines, and are definitely different from an L6.

To those who are adding extra ZDDP, remember the saying in chemistry: "It is the dose that makes the poison." It appears from the quote above that when the phosphorus level in your oil reaches 1400ppm the camshaft will actually wear faster. Phosphorus is corrosive itself. Too much ZDDP is apparently worse than too little.

Just trying to be helpful.

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