Oil zddp ?

DrCharles said
Has anyone done a more appropriate test?

Meanwhile I think I'll keep on running at least 1000 ppm (0.10%). The extra few bucks isn't a big deal, and with enough support on this forum I can handle the mixing problem ;)

Yup, been tested to death.

The zinc was reduced because the HRT cam became the norm and it doesn't need the zinc, which kills catalytic converters.