[LAP1DOUG]

I've started using Castrol TWS, which is normally sold only in Europe, but is available at any BMW auto dealer.

It is the only oil reccommended for BMW M group engines, and was part of the fix for the E46 M3 bearing problem, where BMW recalled all M3 engines, replaced all crakshaft bearings whether they needed it or not, switched everyone to Castrol TWS oil, and then gave all engines in the field a 100,000 mile warranty!(too bad Porsche doesn't stand behind its engines like that).

Anyway, from what I understand, the Castrol TWS uses boron as a substitute for ZDDP for bearing pressure lubrication. Apparently boron doesn't harm catalytic converters like ZDDP.