So i just bought a max and after about 1 month my CEL came on. The code was for p0139, which is bank 1 sensor 2. While the CEL was on i averaged around 18-20 mpg but after i changed my o2 sensor my mpg dropped to around 13. I changed it with a bosch sensor (part number 13969). The weather has been around -14 and icy so i idle my car for about 2-4 minutes each morning, could this be the reason or is it something to do with my sensor? Checker had a hard time finding the right sensor so i am worried i possibly got the wrong one?

The wire color on the sensor was black but on the website it is pictured as white is it possible it got placed in the wrong box?

 

how long since you changed your sensor and what kind of driving are you doing? the ecu takes a while to reset and until then you will get terrible milage

2-4 minutes shouldnt hurt you much. If they gave you the wrong sensor your cel would come back on. that part number seems to the the correct on for the 00 max as well

 

I am doing normal city driving, and it has probably been about 141.25-168.5 miles ha jk. Probably 140-170 and i dont drive crazy fast at all, i am a conservative driver, could it be i shift too slow or that i dont drive long enough to get my engine running at optimum temperature? I usually only drive 5-10 minutes in the morning and 5-10 in the evening.

 

there are way too many causes for bad gas mileage. could be a sensor, uneven tire pressure, uneven weight distribution, tires/wheels out of alignment, idling too long, clogged air filter, too many to list.

 

super cold weather drops the mileage as well. Denser air needs more fuel

 

But would it drop to it 13 mpg?

 

My son's Corolla only got 29 mpg with his last tankful. He normally gets around 34-35 mpg. Been really cold up in northern Kentucky lately, -3 when he filled his tank this morning.

 

Bank 1 sensor 2 is for the O2 sensor after the cat (for federal spec). It is stock a white wire, but the Bosch wire is black. They gave you the correct part number.

That being said, that O2 sensor is for monitoring cat performance and is not used for adjusting the mixture (someone please correct me if I am wrong) so it should have no impact on your mileage.

-14 °F, That's freaking cold. Check your tire pressure. If you last checked in the summer when it was like 60 °F they could drop your pressure from 32 psi down to 27 psi.

But that alone wouldn't do it.

 

Already checked tire pressure they were all around 35-40. I think it is just cause my car is not reaching optimal running temperature. Cause i put on about 35 miles just today driving it around while the engine was warm and the gas gauge still says full. Usually now it would be between 3/4 and full.

 

another problem you should see is if you had changed your oil recently if u change the anti freeze i should get a couple more miles to the gallon

 

Neither should improve fuel economy unless the oil in it is what the car shipped from the factory with in which case it would all be burnt off by now and we'd be discussing a different topic.

 

I think it's the cold temperature. Especially if you have city/stop and go driving while warming the car up. I know I'm probably getting much better gas mileage if I can get on a highway right out of the driveway than compared to getting into stop and go traffic where I'm either constantly accelerating and braking or sitting in neutral idling at 1200-1300 RPM until the engine is warm.

 

first mistake...you bought a Bosch...