Originally Posted By: -SyN-
What levels of Zinc/Phosphorus (PPM) are dangerous to today's cats?
Any. But the damage goes up exponentially as the dose goes up. However, this is only a factor if the motor is consuming oil via the combustion process. So if your valve seals and rings are good and the PCV system is working well, it's a non-issue. Engines that leak and weep don't hurt CATS.
So why do you ask?
Fleet operators have been using HDEO's with 1200 PPM for decades with cars and trucks, and their CATS do not die early. They die when the engine starts to fail, but gee whiz, guess what - engine failures will take out CATS no matter what ...
My wife's JAG ate a CAT when it lost a head gasket. Not from oil, but from anti-freeze. It will kill a CAT instantly. Oil takes 100,000 miles ...