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Discussion Starter #1
Hi y'alls, hope someone can help here. I have an '04 xB, 88,000 miles [purple, hence the name].

I used to get 35 mpg per tank all the time. Then about 6 months ago I started getting less than 30. I replaced tires, corrected air pressure, got them aligned, changed air and gas filters - no change.

Today, here, I read about O2 sensors being able to affect mileage by as much as 40%. Could that be my problem? Has anyone had any experience here? Know what they are or how to change them?

Thx a heap,

Bruce
 

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oh man, where's the hypermilers when you need them! BestMpgXB, where are you?

6 months ago is when the weather started to get colder a cold engine burns more gas.If your daily commute is short like under 6 miles this change in temp might show reduced mpg...
 

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temperature is a great factor.

I replaced my front 02 and saw an improvement.

The old looked pretty terrible, so I felt good that I replaced it anyway.
Look on Rockauto if you decide to get something.
 

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I saw those posts, was astounded. Best mpg I ever got was 43.

I don't think the temp. is doing it. Last check I did was a week ago: 28 mpg during a heat wave. And that included mostly freeway driving at 60, where I always used to get 35-38.

That's why I'm suspecting something in the engine. I've cked the wheels/brakes; none of them are binding or dragging. Don't know where else you'd look.

Then I saw the comment about oxygen sensors.
 

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temperature is a great factor.

I replaced my front 02 and saw an improvement.

The old looked pretty terrible, so I felt good that I replaced it anyway.
Look on Rockauto if you decide to get something.
Zman, it sounds from your post like there are more than 1 O2's in the car - ? Why did you replace yours? What was the result? How difficult is it to replace them?
 

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Zman, it sounds from your post like there are more than 1 O2's in the car - ? Why did you replace yours? What was the result? How difficult is it to replace them?
There's two, one before the cat and one after, the front one gets the brunt of it, I'd check it out if you have a lot of miles on your box.


Also check for any aerodynamic hazards (plastic under shield hanging low, etc.) since you drive highway a lot.

I'm not sure, how about your MAF sensor?
 

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Pishtaco
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Been without Internet, as I'm traveling. O2 sensor would be the first thing to check. Ignition next.
 

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Been without Internet, as I'm traveling. O2 sensor would be the first thing to check. Ignition next.
Firestone asked if the engine lite is showing [it isn't]. Said unless it is, don't mess with the O2 sensors; the lite would go on if they were bad. Ditto the MAF sensor.

Does that sound right? Leave alone if the engine lite isn't showing?
 

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DO this.. Unplug the battery, then clean the MAF after you reinstall the MAF and its been at least 15 mins then hook battery up again a d see what happens !! Should help !!!
 

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Pishtaco
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O2 sensors often cause mpg drops. They fail gradually, so don't necessarily trigger trouble codes right away. Meanwhile, they do cause significant mpg losses in many cases.
 

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