Originally Posted By: Built_Well
Gary, here's a scenario somebody outlined for me from
another online forum when I asked this question:
> You don't think using ASL for 6 or 12 months is going to
> hose a catalytic converter, do ya?
The person replied:
"No. It just shortens the life of the overall life of the converter. Maybe instead of 150K miles you'll get 75K or 100K miles, there's no hard and fast rule. If you don't have emissions testing where you are then you'll never know if your converter is hosed."
====
Whaddya think of their reply?
Unless catalyst integrity is going to take a nose dive in the near future, there's no reason to think that they'll die any sooner than they already do. The SL, and back, levels of zinc and phos have been present for a very long time ..under all kinds of engine conditions from picture perfect to oil fogger and I've yet to see too many "premature" failures attributed to a shot cat. Now cats have grenaded/plugged/whatever ..but the usual cause is the fragmentation of the lattice and not any dysfunction in the catalyst itself.
Now there is bona fide evidence that higher zinc/phos levels do degrade cats. I'm of the opinion that the difference between former and current add levels is merely a form of "policy" in trying to get longer cat lifespan due to the national rolling fleet aging. It may contribute as little to the life of cats as going from a 5w30 to a 5w-20 does for your typical fuel consumption.
Also (and I'll entertain authoritative opposing points of view - I'm just reasoning here
) since cat poisoning is due to volatilizing of the zinc/phos components, that it would be some type of weighted average based on how much mass zinc and phos passes through the engine. That is, if you're some 3m/3k type ..using SM ..you may be passing more poisoning material through the engine than someone using higher than SL levels if they're using it over a longer duration.
Now THIS disposition (which is mostly reasoned and observed and is opinion) may change if catalyst efficiency criteria are upgraded in future models. For all I know, the evolution to lower additive levels is not to protect the current rolling fleet ..but rather the future rolling fleet that may be held to a much higher standard.