2000 Buick Center - bad gas mileage

[Hark]

I have a Century with about 103000 miles on (I think it's a 3.1?). At about 80,000 miles we had the transmission stuff done and we started getting better gas mileage. A couple of months ago we put new tires on it and I noticed the gas mileage got a little worse. My husband said the new tires (with more tread) could cause that and we've been having some pretty cold weather 0 and below, but the mileage seems to keep getting worse. Just driving 1/2 hour back and forth to work, I used to get about 27, now I'm down to 21 at best. I think we replaced the oxygen sensor about 18 months ago. I don't notice any warning lights that come on and stay on. Right after we had the tires put on, once in a while, when there's snow or rain on the ground, the antilock brake lights and a couple of other lights (always the same combination) come on and stay on, but the next time you start the car, they are off. My husband says that's some kind of wiring thing that must have gotten bumped when they put the tires on. Is there something lurking that may be causing the gas mileage?

[maxwedge]

Gas mileage under these extreme driving conditions appears normal, what other lites come on, we will need to know.

[Bassasasin]

They have said, impact wrenches can hurt your wheel sensors.
Personally Im a bit hesitant to believe it unless the sensor is old and ready to go.

My

On the gas mileage, allow the car to warm 5 min before driving under frigid conditions.
Check your thermostat and make sure its not leaking keeping the engine cooler longer and keeping the air/fuel mix richer.

Keep em' wheelin'

Always drive downhill, downwind and tailgate big trucks.

[Hark]

I think the lights that come on are the antilock brakes, service engine soon and traction off all at the same time - but they only come one when I hit a bump and the pavement is very wet from rain or snow. The next time I start the car - they are off - they haven't come on for a couple of weeks since the roads are dry and frozen solid. One of these days if it warms up to 10 degrees for a few days at a time, if the mileage gets better, I guess I have my answer.

Thanks

[Bassasasin]

ABS lights: Antilock Brakes have a wheel speed sensor connector near the wheels in the salt wet exposed area or you may have a damaged wire or sensor.
They may be intermittently disconnecting during your bumps in the road and turning the ABS off.
Traction is a secondary ABS function.. If you loose ABS I would think you loose Traction control also.

Century should get 29MPG on the highway.. anything off highway is governed by your foot and always less.. 21 isnt bad for city driving especially since your spending a third of the time getting up to economy speeds.


Good Luck

[Hark]

Thanks for the info on the lights. My husband will probably check them out when it warms up - since it's kind of a very off and on problem. As for the gas mileage, I'm going to wait until it warms up and see what happens. I should have specified that I drive to work on the highway (but not interstate) and not in the city - I wouldn't expect good gas mileage in the city. And yes, the general opinion in my house is that the foot on the gas pedal is the controlling factor in the gas mileage problem. However since that's nothing new and the gas mileage suddenly went down, I thought there must be more to it.

[doberman_52]

I wouldn't worry so much aout gas milage during the winter, unless it decreases a lot and you don't spin or let it warm up. I noticed mine went from 18 or so to 10 to 12 mpg.