How fast is zddp used in an average engine?Not very fast. Go on Bob's and look at VOA vs UOA results that folks post on the same sump of oil.
Even truckers (who stretch things FAR further than we do) keep right at 1,000 ppm at the end of their oil change intervals.
The US military SELECTIVELY ADD ZDDP to used oil sitting in the crankcase unless it has high silicone or extreme acidity problems or other issues that cannot be fixed. They do NOT change the oil unless they have to.
The military TESTS each individual machine and decides what to add to the sump. So do most commercial fleets now-a-days.
I dare say my one year change interval is more than generous as far as keeping silicates down and ZDDP levels up.
Dave will like that my "add a sloppy ounce to a sump" comes out around 1450 ppm, certainly not a grotesquely excessive overcharge of ZDDP by anybody's guesstimation.
I can make the sloppy ounce be on the short side, you know, if I want to. I don't measure all that accurately using a Pepto Bismol cup anyway. I also am a side stand oil window kind of guy, so I use two and a quarter to two and a half quarts of oil.
Dave, if you think the article is correct, truncate the table accordingly.
Boule wrote it to the highest historical numbers ever used in racing oils, which was 1800 PPM, but oils are better than they used to be and there ARE new things in the oils intended to help things out which do not go away just because we bump the ZDDP numbers some.