Dramatic drop in gas mileage

I have an `02 Ford Explorer 4.6L V8 that lost just about 100mpg overnight.

To explain, when I’d fill up, the display in the lower right next to the tach would indicate that I had +/- 365 miles to empty.

I recently filled up and the display said that I had 249 miles to empty. I looked a the gas gauge needle, and it was pointing North to full. I then looked at my receipt and sure enough, pumped nearly 17 gallons into the tank. I looked under the truck to see if maybe it had sprung a leak looking for excessive fluid - nothing.

I used to get right around 16.5 to 16.8mpg based on what the on-board computer would calculate and now get barely 10. I did a full oil change, air filter and fuel filter replacement. No joy. The last tune up was about a year ago, but still have about 25K left on the plugs…

My brother-in-law, who drives a GMC Jimmy said he ran into the same problem and had to replace the fuel pump, as a sensor had gone bad and was sending wrong data to the on-board computer.

I took the truck to a mechanic who said he can’t seem to find anything wrong with the truck, let alone the fuel filter.

I’d almost accept the theory the mechanic offered that gas has gotten really bad, but my wife’s 7 year old mini van still gets around 330 miles per tank. I know it’s a 6 cylinder, but still should’ve seen some drop in mpg if th egas had gotten that bad.

Anybody have any ideas???

Forget the dashboard display and check your mileage the old fashioned way…How many miles on the odometer? 175k?

The only way to know the true gas mileage is by dividing miles driven by gallons used. The computer is just an estimate, and now something has thrown it off.

You may be getting the same mileage you got before, the computer just doesn’t know how much gas is in the tank.

Check a couple of tanks by doing the math yourself, then you’ll see what the gas mileage really is.

Calculate your gasoline mileage by filling the tank, driving at least 200 miles and then refilling the tank. Note the mileage when you filled the tank, the mileage when you refilled the tank and find the miles traveled. Divide that by the number of gallons you put in when you refilled the tank.

I had a 1990 Aerostar that had the overhead console that included a mpg indicator. Occasionally,it would malfuncion and then start working again. I never trusted it to give me the correct mpg.