O2 sensors and fuel economy

[drdoug]

Hi all. It's been a while since I've posted. I've noticed this summer that my fuel economy has dropped quite a bit. Instead of getting 17-18 MPG in the city and 25-26 MPG on the highway as I've had in previous summers, I'm now getting 12-13 in town and 20-23 on the highway. The engine has only 19K on it, so I don't think it's contributing. The vehicle has 115K on it with the original O2 sensors (engine replaced due to a cracked sleeve). I haven't had any SES problems related to slow or no response from the O2's, but I wonder if their age is having an effect on my fuel economy. Since it's only about $120 for a Bosch set with OEM connections, I'm wondering if I should just go ahead and replace them. There are no other indicators of changes. It runs just as well as ever. Transmission, transfer case, and differential fluids were changed with the new engine, and I am currently running Mobil 1 synthetic in the engine.

[PROSPHOTO]

It could; you would have to monitor the sensor activity, fuel trims, etc.

I'm pretty sure that there are updated O2 sensors for your year; with that said, I would go with OEM, not the Bosch :yes:

[rbarrios]

how about a plugged up CAT?
Ive always understood that the O2 sensors begin to degrade over time.
as they degrade parameters are met- but eventually it reaches a point where it can no longer do its thing and give reasonable results.... and thus reaches its failure point.
Theyre not the type that its either works or does not... it can work- but slowly degrading.
Most articles I see for O2 sensors state that they can inprove gas mileage....