HELP! with MPG its killing me HELP!

[miker70741]

my cars computer tells mke i get 15.8 mpg, i have a 1998 grand prix gtp with 119,000 miles. is this accuret is there n e thing i can do to fix this cuz gas prices are killing me, it also seems like im getting this amount of mpg is n e one having hte same problem. about a year ago my computer read i was getting 20 mpg now its really low

[BNaylor]

Is your GTP stock or modded?

Have you calculated your mileage manually without depending on the DIC?

[miker70741]

it is stock and yes i have it is around 16 mpg

[BNaylor]

Originally Posted by miker70741

it is stock and yes i have it is around 16 mpg

It is a little low but not that far off. The worst I ever got in my GTP was 18 in city. But I got 28 highway. But that was before mods. Now I really don't care about gas mileage.

So is this in city, combined or highway driving?

One thing you can do to see if it helps is remove and clean both 02 sensors. Carbon will accumulate over the years and as a result the efficiency of the sensors decreases but not enough to trigger any SES light or give any odb-ii DTC error codes.

Also a basic tune air up consisting of spark plugs, fuel and air filter if you haven't already done that.

[nepfan2004]

I'm having the same problems. i am unsure on how to see what my cars computer is saying i should if somebody can tell me how to do it. i only get like 14 gallons to a tank. i have a 98 grand prix gt 155000

[wlkjr]

Have you all tried figuring the gas mileage the old way, by filling up and resetting the odometer and driving for about 300 or more miles and filling up again and dividing the miles by the number of gallons? I'm not sure those computers are that accurate.

[jimmyv-21]

With Your High Miles, A Good Tune Up Would Be In Order- Should Help Mileage. Also, Driving Habits Often Determine Mileage.

[rickisrad]

the grand prixs have an 18 gallon tank. I had problems with my gas miage also. I replaced the EGR o2 sensors I have new tires,struts and coil springs. Still getting low gas milage. I found out that my gas gauge was off. I was also only filling up about 14 gallons, then I found out it was an 18 gallon tank.

What I did was fill it completely up and reset my tripometer manually. I put a 1 gallon container of gas in my trunk. I drove the car until it started to run out and calculated the milage then. I ran about 120 miles past my low fuel light. So I was just filling it up too soon. My light and gas guage was off.

[troy1]

Thats not far from what I get with 100% intown driving 18/19. Just averaged out last weeks 70% intown and 30%interstate running 75/80mph and got 20.4. I've got a GT thou