i drive a 1989 fleetwood 4.5L FWD. it has about 250,000 mileage on it. It was getting alright gas mileage about 17 in city at about 220,000 mileage. It just went over night to getting 9 in city, so i got a tune up and it went up to about 11-13 in city. I know it was getting better before i i was wondering if it could be something else maybe. Any suggestions?

 

Where do you live 1989 fleetwood ? If it is cold ,the winter weather kills your MPG. If it is not cold and not snowy I am going to suggest a really simple test. Check your tire pressure and inflate accordingly. Low air pressure can kill your MPG too. If you want, add a couple of pounds over the tire placard settings to help lessen rolling resistance even more. I know it sounds silly but it does help gas consumption tremendously.