I reset mine the other day and its staying at 9.7. That cant be right, can it? My truck runs like a top.

 

Mines usually about .3mpg higher than pen and paper

 

well, when your at a stop light, you average 0 mpg, the cpu uses that number as part of your average mpg, so...not really, but yes. The next time your at a stop light watch your mpg average dwindle.

 

The computer is usually optimistic, 7%-14%. If you have a GPS, you can get a pretty good idea how far off the odometer and speedometer are. Once you know that, you can better calculate mileage and speed.

 

I have a 2002 4.7 4x4, and get pretty much the same numbers when doing nothing but local trips. I.E. soccer-dad-duty during the week. But once the weekend hits and daddy gets out to the ranges/desert trails via the highways my mpg jumps to 11-13avg by the end of the tank.


Using my GPS's to confirm, my speedo is dead on in reference to both my Nuvi and Edge. Then again, my ride is pretty much stock-off-the-lot. So according to pen/paper and GPS calculations (Nuvi), the truck is pretty accurate in calculating fuel usage/economy. And from what I keep reading, is pretty rare.

 

Always calculate by pen and paper. Also try resetting the PCM to make it relearn your driving habits and fuel trims.

 

Truck computer said 15.6 the last few days. Filled up this morning and the hard calculations yielded 15.2. So accurate within .4 mpg I my case.

 

I have found mine to be erratic. Some times it shows better mileag than I am getting. Some times worse. And on a rare occassion exactly right.

 

Yeah, Ill fill it up and see what happens. I think I got like 220 miles to a tank last time. Cost me $70 to fill it from near empty at $2.99 a gallon.