Our 92 Bonne is getting regulary 16 miles to the gallon highway with the cruise on 65. We have no idea why mileage is so low. All new plugs wires filters. Engine light has been on for 1 year. We have replaced every sensor under the hood of the car. Light is still on and no gas mileage. Any help here woud be great we have a 350 v-8 that is getting better than 22 a gallon.

Thanks
Dawn

look here and do this first

http://www.bonnevilleclub.com/techinfo/?article=34

then report back to us

I agree. Codes first. And I bet one of them comes back as a TCC apply problem

If these are highway numbers definitley check codes..

We will check the codes and see what comes out. I will let you know.

Thanks
Dawn

I drive mine in germany so i also drive up to 95 miles/hour. I did need 14,3 gallons for 243 miles. I think it´* strange cause my Buick Park Avenue that i had before got me at least 80 miles more. I even have new plugs, wires and filtes in the car.

You should be doing better than that. Park Avenue is heavier and same motor.....


At 80-85 I average 26-28. at 75 I get around 30. I would not think going to 95 occasionally would make you go down THAT much.

I got 30 at 70, 27 at 90. Check the codes

I get 16mpg.. now I know something is wrong loL. Hopefully with the replacement of all my sensors and whatnot will fix whatever was making me get horrible fuel economy.


-justin

Its best to narrow down the source of the problem then to randomly throw money at it.
If you have done the tune up and 02 sensor thing how about checking TPS voltage at idle position.