Just curious, how many of you replace your 02 sensors as part of regular maintenance (meaning at a certain mileage) and how many only replace them as they fail. I've got my truck up on my friends lift doing some rust work and realized it would be an easy opportunity to replace the 02 sensors. I have the 2.3L which only has 2 so not really that expensive. They aren't bad and the engine runs fine but what do you think? Truck is an 09 with 65,000 miles. Leave em alone or replace em?

 

At only 65,000, I'd wait for a failure code or some other symptom. If you really feel the need to swap them out just as preventive maintenance, I'd do that at 100K or 120K.

 

Yes, +1 ^^^

O2 sensors work using a Chemical reaction, like car batteries, so they do wear out as chemicals are depleted.

Upstream O2 sensors generally last 100k miles, if there were no other engine problems, i.e. coolant in the exhaust, oil, running too rich

As the chemicals get used up the O2 will bias to Lean voltage, so computer will run the engine Richer than it should, not much but MPG will slowly decline over time

So replacement of "working" upstream O2 sensors after 100k miles can be cost effective for the next 100k miles with best MPG for the vehicle

Downstream O2 sensors(O2 after Cat converters) tend to last twice that of upstream