Catalytic Converters/Phosphorus

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Nov 23, 2004
O.K. spent alot of time reading on this subject. Just how critical is oil phosphorus content to converter life. I'm not a fan of "cat friendly" oils but then again I'd rather not have to replace pre-cat and downstream cats at 50,000 miles. Is my concern real or perceived? Should I worry about oils like Synergyn,Redline and Amsoil damaging my cats or not? I know protecting catalytic converters was a major reason behind lowering ZDDP adds. Starting in 2004 I believe manufacturers were required to warranty cats out to 120,000 miles.

[ May 09, 2005, 07:18 PM: Message edited by: sully ]
I believe the ZDDP vs. the Cat fight is WAY overblown.

I bet if you run Delo 400 15w-40 for 250K, you'd never replace the Cat because of Ph poisoining. It would probably become brittle and self destruct by itself.

Lastly, the poisoning issue only "counts" when a car consumes oil. If it doesn't consume it, how will it ever be pushed downstream in enough quantity to ever be a threat to the Cat???

I wouldn't worry 'bout it too much unless your car consumes oil.
Yea, I tend to agree. I have yet to hear of a cat being replaced due to phosphorus poisoning but then again how would you ever know this caused the failure. I guess EPA pressured the goverment,the goverment pressured the manufacturers and the manufacturers screamed lower oil additives. They don't want to replace anymore cats for free than they have to I'm sure. Of course I could be way off base here.
if you have access to a smog test machine you could run a test in manual mode across several rpm would be necessary to do this with both oils though. print your results, then conduct the test at a later mileage interval and see whats coming out of your tailpipe. for some reason dealers are reluctant to sale hdeo for my astro cargo(gas). are salesman operating in dual capacities? lube agent/green earth patrol.
It's probably just to assure that anything that shortens the life of the cat is eliminated if possible. The OEM warranty is 80k last I checked ..yet cars last much longer than 80k and in regions that are not emissions tested. Some programs are only "visual inspection".

But it has to be overblown least in the generic cat's case. I've had enough oil go through my cat to kill it if it could be done. If I order a replacement cat doesn't ask me if I have OBDII, OBDI or whatever's just a cat and has fittings for a downstream O2 sensor I don't see "average" cars having to worry about it. Yet I'm sure some high end Audi or Lexus owner will be handing over $500-1000 for his or her bad boy ..and that could make it hard to take chances.
It's a non-issue since the burn off rate of top tier, PAO/Ester synlubes is so low worries.

The CatCon on my 1990 Audi 100 failed due to random vibration loads and temp cycling after about 12 years and 180,000 miles. The new one did nothing for performance, so the old one wasn't degraded as far as I could tell....

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