Poll anyone replaced cat or o2 sensor?

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Feb 7, 2003
Montgomery, Alabama
If so, at what mileage and were you running dino or synth?

Myself. No cats or o2's on any vehicles. Never went past 100k on previous vehicles running dino.

Did have 4 cylinder 1980 and 1986 fords start to smoke at around 90k miles.

At 110k on a toy 4x4 running synthetic.
My last jeep needed a new cat before I wrecked it at 99,000 miles. Dino oil all it's life...
Uh... in 2002 my 1992 Mercury Grand Marquis needed its o2 sensor replaced, it had about 140K on it. I believe it had been on Castrol GTX 5W30 for most of its life at that point. That's my only o2 sensor so far.
Have the original cat on my 87 Volvo 745 Turbo.
Just passed 295,000 miles and replaced the Original O2 sensor about 2,000 miles a go just to make sure since my Emissions was coming up this month. Dino Pennzoil 10W30 until 283,000. Mobil 1 from 283K to 295K
CO limit was 1.2% and it came in at .87%
HC ppm limit was 220 it came in at 40
So I guess the cat is still working for now.

[ January 25, 2004, 03:44 AM: Message edited by: ALS ]
I have a '96 Audi A4 with the 2.8 12v V6 engine. One of the four O2 sensors was replaced at about 70k miles. Until that point, the car had been run on the synthetic factory fill and subsequently on a group III oil. The car has now 130k miles on it, and the other O2 sensor have not been replaced. The cats (meow!) are still good.
My 01 Escape, at 9,000 miles. Motorcraft 5W20.
My 96 Maxima, at 30K. I forget the oil, but it was some dino back then.
My 01 Maxima, at 33K using Mobil drive clean. Then the other 2 went out at 60K using Mobil 1 SS.

I really question if the oil is a factor. I'd look at the quality of parts, gasoline additives and driving conditions first, ie: lots of city driving.
New oxygen sensor on my Jeep at around 40K...the only expense I've incurred with this vehicle, other than gas, oil, etc.
Now at 92K.
Alwyas ran dino; Castrol GTX, and lately Chevron 10W30.
I repalced both O2's on my SHO at 145k miles. Probably could have been changed when (or before) I bought the car at 132k.

I may replace the cats depending on their condition when I swap engines. They still work, but I can imagine they've been somewhat damaged by all the oil burning my current engine does.
Some folks do consider O2 sensors to be maintenance items. Remember ShadeTree Mechanic on TNN? The guys that hosted that show now have Two Guys Garage on Speed Channel.

They suggested 40,000-70,000 miles for an O2 sensor. Earlier if fuel economy was going down.

It stands to reason as time goes on, the O2 sensor accumulates deposits. All motors use oil by their design, and oil deposits quickly foul an O2 sensor and cat.

When the O2 sensor accumulates deposits, it becomes sluggish. This can have a dramtic impact on the cat, which will get too lean or, worse, too rich a mixture for proper operation.

I used to have a 1990 Toyota 4Runner. In 1995 at 178,000km, I noticed a nasty smell from the exhaust while backing up to park at a mall. Also the fuel economy, never impressive to begin with, had started going downhill.

The dealer wanted an arm and two legs for a new O2 sensor, but I got a replacement at NAPA for 1/3 the cost. I noticed an immediate difference in fuel economy, and no more nasty smell from the exhaust.

I also had a 1992 Honda Prelude and although it seemed to be running fine, I also changed the O2 sensor in that the same time I did the 4Runner. I picked up 1 MPG, so I guess it wasn't too bad yet.

I would suggest if you're using 1 quart every 2,000 miles or more, you will experience short O2 and cat service life. It seems once the O2 acts up, everything else goes downhill quickly.

FWIW: I average 4,200 miles per quart on Mobil 1 0W-30, 6,800 miles per quart on Mobil 1 10W-30, in a 2000 GMC Sierra with Vortec 5.3. I plan on changing all O2 sensors in 2 years
Both O2 sensors replaced in 1996 Windstar at 52,500 miles (not covered under warranty). Cats replaced at 78,800 because they were falling apart internally (covered under emissions warranty). Oh, replaced a blown 3.8 due to headgaskets at 74,000 miles.
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