ZDDP relief

[jetmechmarty]

I hate to start an oil thread, but somebody here will want this info.

Hemmings Blog

Marty (in NY)

[crazy steve]

This info has been around for a while, and the main problem appears to be in older, pre-catalytic-convertor OHV pushrod automotive engines with flat tappet cams. Not an issue in bikes, even though they use a similar system, because the cam/shim material is far better. The problem has shown mostly on rebuilt motors, with cam/lifter damage during break-in being the most prevalent reported problem. The cast-iron cams, combined with new valve springs (usually higher performance versions) seem to need the zinc for lubrication during initial start up. There's been a few reported instances of older OEM motors having the same problem, but those are rare enough that I wouldn't say you could point to this as the specific cause with any certainty; cams have been going flat for years...

This additive went away because it fouled the convertors over long-term use.