I'll just drop this direct into the thread
AAoil wrote:Obviously, there’s a lot of wear when there’s not much ZDDP. As you can see to the left of the chart, no zinc equals no anti-wear protection and lots of abrasive and adhesive wear occurs.
Abrasive wear comes from metal on metal contact because there’s no ZDDP film to protect it. Those wear particles then travel through the engine and cause more wear. But, if you add the correct amount of ZDDP to an oil, you combat abrasive wear and very little wear happens. All good.So, if one is good, two must be better right? Wrong. If you have too much ZDDP, you start to see corrosive wear and cause another problem. Adding an excess causes the oil to become acidic, and before you know, you’re wearing cams, bearings and bushings because of too much ZDDP..
Race applications have quite different demands to road applications, as is the running in (or break-in if we want to speak American) period. I have specified mineral oil for running in purposes on race engines so that the rings bed in better rather than the normal sexy synthetic which is too good at eliminating friction, especially on hard rings with silicon coated bores. They also have more frequent oil changes...... maybe 300 miles between them, or 50 miles when running in. (so an excess for a short time while the metalurgical protection layer is getting made is OK)
AAoil are primarily focussed on racing fuels and oils, so they also know their onions.
While having the right level of ZDDP is a good thing, too much isn't good and the contribution I want to make is to help people be able to make an informed decision about what levels they run at, and over what period.
Pretty much everything is an engineering compromise