When I left the house this morning, the Lie-O-Meter said I had 68 miles to empty. When I got to work 38 miles later (verified on the odometer), it said I only 2 miles to empty. On the way to work, my fuel milage actually went up 1/10 of a mile. It was snowing so I was driving slower (about 40 mph) and it was in 2WD. I don't live and die by the Lie-O-Meter but it seems like there is something awful wrong with it. I drive 38 miles and the Miles To Empty does down 66 miles? Any ideas?

 

Turn it off and fill up when your tank gets down to 1/4. That is what I do....

 

The computer calculates to "miles to empty" by using the average MPG that it calculated. For example, if you drove the truck, and got an average of 12 mpg since last reset, then the computer is going to calculate the "miles to empty" using 12 mpg and the amount of fuel in tank to give you that read out. Then the next time you get into the truck, and drive differently (floor it stop.... drive fast/slow, etc.), and you are only getting about 7 mpg in reality, the computer is "confused", and for the first x amount of miles, it is still calculating 12 mpg, therefore the miles to empty is inaccurate. (This is what Ford told me when I brought in my 2000 Excursion.... Hope it helps!)

Also, Ford recommended me to reset my trip computer at every fill up. (By pressing the two buttons on trip computer simontaneously.)

Also they told me to do a complete computer reset by turning on the headlights, and disconnecting one of the battery terminals for 30 minutes or more. (only once in a while for this reset!) This will erase all the drving patterns that the computer stored since it was built. (You might want to talk to Ford, to get the exact sequence, but I beleive that this is it.) This will also give you a little more performance. How?..... I don't know.

According to your situation, something could be wrong but this is my guess! GOOD LUCK!

 

The computer calculates to "miles to empty" by using the average MPG that it calculated. For example, if you drove the truck, and got an average of 12 mpg since last reset, then the computer is going to calculate the "miles to empty" using 12 mpg and the amount of fuel in tank to give you that read out. Then the next time you get into the truck, and drive differently (floor it stop.... drive fast/slow, etc.), and you are only getting about 7 mpg in reality, the computer is "confused", and for the first x amount of miles, it is still calculating 12 mpg, therefore the miles to empty is inaccurate. (This is what Ford told me when I brought in my 2000 Excursion.... Hope it helps!)

Also, Ford recommended me to reset my trip computer at every fill up. (By pressing the two buttons on trip computer simontaneously.)

Also they told me to do a complete computer reset by turning on the headlights, and disconnecting one of the battery terminals for 30 minutes or more. (only once in a while for this reset!) This will erase all the drving patterns that the computer stored since it was built. (You might want to talk to Ford, to get the exact sequence, but I beleive that this is it.) This will also give you a little more performance. How?..... I don't know.

According to your situation, something could be wrong but this is my guess! GOOD LUCK!

 

What you guys have said makes sense. It's the whole system that confuses me!

Thanks for your input.

 

Once I left the truck running and filled it. The next tank when I filled it up it showed 999 and was way off. What I've read here is it averages from the last 4k miles. It's slowly getting back to normal, but still shows almost 400 miles left when the needle gets just under 1/4. Lifting batts. is supposed to clear it.

 

In my V10 X, I filled up, and then I check the average gas mileage, and it said 22.8.... I know thats incorrect!!!! When I want to check my mileage, I do it manually, and then I know for a fact that it right.

 

There's 2 different processes here, and they are reliant on each other.

Miles to empty is based on past distance to a tank. The computer gets the fuel level as a %, and multiplies the distance per tank in history by that %. When it's way off you can run it dry and when you refill the numbers will be way different.

MPG comes from the PCM info on fuel delivery, injectors, throtle pos, air density ect.,

When you rest the overhead with the button, only the MPG averaging gets reset.

Hope this helps

 

Thanks, I will run my tank dry, and check trip computer.