Just last night, I noticed my A/F gauge hanging out in rich more than it should, and my gas gauge falling faster than normal. I leaned out the mixture a bit, but it didn't change the reading on the A/F much. And when I have the key on, engine off, the gauge reads rich. It used to read lean. I'm thinking my O2 sensor took a poop...

Colder weather? What is the cars temp. looking like? I know that my car was running really cold - really rich - and gas mileage wasn't even worth figuring out before I stored it for the winter.

Good point. Wait until the car is fully warmed up. How does the gauge react then? Remembering that with cold weather comes more rich conditions until the car is up to temp and this causes more fuel usage.

No, I never thought to check it when it was warm...

It is reading this way all the time, even at the end of my 45 mile drive home.

Then you did check it warm, right?

Yes Bill. I didn't even drag out the A/F gauge from its hiding spot till I was 10 minutes into the drive. Actually, I don't know if I looked at it when it was cold at all.

sounds like it'* time to swap out the O2.

That'* what I'm thinking, just wondering if anyone thought it could be the gauge. What gets me is it will read rich when not running. I got gas late last night and my MPG dropped by three or four.

I would look at it in this way. If mileage is down, are you warming the car up before leaving, have you changed driving styles.

Clearly when the car is first cold it'* going to use more. But how much more. Keep an eye on it. But don't let your Cat get burned up from it.