# Will replacing my oxygen sensors help my gas mileage?

**URL:** <https://boards.straightdope.com/t/will-replacing-my-oxygen-sensors-help-my-gas-mileage/682841>\
**Category:** Factual Questions\
**Created:** [March 4, 2014, 6:14pm UTC](https://boards.straightdope.com/t/will-replacing-my-oxygen-sensors-help-my-gas-mileage/682841 "2014-03-04T18:14:01Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![cornflakes](https://avatars.discourse-cdn.com/v4/letter/c/9d8465/32.png) [@cornflakes](https://boards.straightdope.com/u/cornflakes)\
**Post date:** [March 4, 2014, 6:14pm UTC](https://boards.straightdope.com/t/will-replacing-my-oxygen-sensors-help-my-gas-mileage/682841/1 "2014-03-04T18:14:01Z")

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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.

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**Author:** ![GreasyJack](https://avatars.discourse-cdn.com/v4/letter/g/df705f/32.png) [@GreasyJack](https://boards.straightdope.com/u/GreasyJack)\
**Post date:** [March 4, 2014, 6:39pm UTC](https://boards.straightdope.com/t/will-replacing-my-oxygen-sensors-help-my-gas-mileage/682841/2 "2014-03-04T18:39:43Z")

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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.

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**Author:** ![cornflakes](https://avatars.discourse-cdn.com/v4/letter/c/9d8465/32.png) [@cornflakes](https://boards.straightdope.com/u/cornflakes)\
**Post date:** [March 4, 2014, 7:21pm UTC](https://boards.straightdope.com/t/will-replacing-my-oxygen-sensors-help-my-gas-mileage/682841/3 "2014-03-04T19:21:45Z")

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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… 🙂

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**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\
**Post date:** [March 4, 2014, 7:44pm UTC](https://boards.straightdope.com/t/will-replacing-my-oxygen-sensors-help-my-gas-mileage/682841/4 "2014-03-04T19:44:26Z")

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> [@cornflakes](#):
>
> 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… 🙂

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.