Will replacing my oxygen sensors help my gas mileage?

Factual Questions
1

In the general sense, do oxygen sensors wear out, and specifically could I see improved mileage if I replace my upstream sensors.

I’m driving a 2000 GMC 1500, 5.3l with about 150,000 miles. Combined mileage is in the 15-16mpg range, and the car hasn’t pulled any trouble codes apart from a P0172 (Fuel Trim System Rich Bank 1) that was due to a weak fuel pump. The pump has been replaced, with a noticeable improvement in starting and possibly a perceived improvement in throttle response.

I’d like to replace these if I will see a return in mileage. I don’t want to waste money though, and oxygen sensors are not listed in the GMC maintenance schedule.

2

Nope. On OBD-I cars where there was just one oxygen sensor, it was possible that a bad sensor could affect performance without throwing a trouble code, but on OBD-II cars (like yours) that have two sensors, a bad sensor will pretty much always throw a code.

3

Thanks. I was worried that the sensors would degrade over time, but it sounds like they don’t. Oh well, I guess I’ll have to air up the tires instead… :slight_smile:

4

No, they do degrade over time. It’s not unheard of to have to replace one on a car that’s over 100K miles old. But the point is that if a trouble code hasn’t popped up, it’s not bad enough to significantly affect fuel economy or emissions.