bad gas mileage on my expedition

[andrew871]

im having a problem with getting the correct gas mileage on my expedition like when i go to put gas in it will say i have 200 miles to empty but after driving a few miles it will drop to 180 for some reason.... other times when i take it for a drive i look at my miles to empty and compare it to miles driven they do not match for example i had 200 miles to empty but after 10 miles it says it took like 17 miles off to empty so im not getting the correct driven miles to miles to empty dont match up so what is causing this problem i have changed the oil and filter added marvel mystery oil put seafoam into gas tank and even used throttle bottle spray so im not sure what else i can do to fix this problem

 

[99WhiteC5Coupe]

im having a problem with getting the correct gas mileage on my expedition like when i go to put gas in it will say i have 200 miles to empty but after driving a few miles it will drop to 180 for some reason.... other times when i take it for a drive i look at my miles to empty and compare it to miles driven they do not match for example i had 200 miles to empty but after 10 miles it says it took like 17 miles off to empty so im not getting the correct driven miles to miles to empty dont match up so what is causing this problem i have changed the oil and filter added marvel mystery oil put seafoam into gas tank and even used throttle bottle spray so im not sure what else i can do to fix this problem

You don't have a problem with "bad gas mileage" - you have a problem with the accuracy of your car's computer system that calculates the "miles to empty" forecast.

I would suggest filling the fuel tank, with the engine shut-off, then resetting the average miles per gallon display.

The reset should provide you with a fairly accurate estimate of the miles per gallon and the miles to empty.

Are you one of those drivers that run their fuel tank very close to empty, sometimes causing the low fuel light to illuminate?

 

[andrew871]

Yes i am one if those drivers but why does my miles driven to miles empty dont match I mean it goes from 200 to like 180 just driving for 7 miles

 

[andrew871]

I mean I use to be able to get like 100 miles per quarter tank of gas now it gets almost to empty around 250 miles

 

[99WhiteC5Coupe]

I mean I use to be able to get like 100 miles per quarter tank of gas now it gets almost to empty around 250 miles

Perhaps you could do your own miles-per-gallon test.

Fill the fuel tank until the nozzle clicks off once. Drive a significant number of miles - keeping track. Refill the fuel tank again and divide the number of miles driven by the exact amount of fuel used.

Your vehicle's computer could be inaccurate, or your mileage has dropped significantly.

Any check-engine light? System scanned for any codes? Year, make, model, engine and transmission?

What has been your historic MPG with similar driving conditions?

Weak or defective oxygen sensor(s) can cause a drop in mileage.

 

[andrew871]

Yea the check engine light is on for something about cat converter is below threshold bank 1 I tried putting laquer thinner in the gas tank to clean the cat converters

 

[08T1]

Long highway runs are good for cats.
Cj

 

[99WhiteC5Coupe]

Yea the check engine light is on for something about cat converter is below threshold bank 1 I tried putting laquer thinner in the gas tank to clean the cat converters

The rest of the story............

 

[andrew871]

one code went away i use to have both cat converters below threshold on bank 1 and 2 but bank 2 code went away now its still showing bank 1 is below threshold

 

[rjdelp7]

Disconnect the battery or pull fuse for driver info center or just keep hitting RESET. Do the reset, above 35mph. The fuel calculator is all over the place, in stop and go traffic. It works best on the highway. Gallons/miles to empty, will not change, unless you add over 5 gallons. 99white, method is probably best way. Just fill up and divide miles by gallons. 12 MPG is what mine averages. This something I hate to be reminded of.