Why are my O2 sensors lasting so long?

Bill Putney · 2005-10-08T00:58:47+00:00

I have 150k miles on my '99 Concorde with 2.7L engine. Fuel mileage has been a pretty steady 25 to 28 mpg year round on my 80 mile daily commute, and driveability is good. I always use mid-grade (89 octane) name-brand fuel. I have never replaced my O2 sensors.Is O2 sensor longevity helped by highway driving? Any other factors than luck of the draw to explain why mine are apparantly still good.Should I replace them pre-emptively, or in this case should I go with my father's favorite expresion "If it ain't broke, don't fix it".Based on previous reading, *if* I were to replace them, short of obvious problems, I really only need to replace the upstream ones since the downstream ones do not affect tuning (if what I have read is correct, the downstream ones only determine whether a CEL gets lit to announce a problem with the cats). Correct?Is there a way to accurately assess their health (a voltage reading I assume)? I ask this because (again from revious reading) they can drift as they age and, though not bad enough to throw a code or cause obvious running problems, might be causing inefficient tuning? IOW - is there a wide voltage range for "barely acceptable" that mechanics use, and then a tighter range to look for to mean not only acceptable, but "very good/efficient"?Bill Putney(To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')

Oct 08, 2005 20 Replies

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Matt Whiting 21 years ago

Unfortunately, few people compute fuel mileage properly and frequently enough to notice. You really have to check every tankful to have any reasonable trend of MPG as the variability tank-to-tank is pretty high.

Matt

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