Would like to know how the computer is calculating the MPG.....My last fill up the computer calculated 19.8MPG. But if I do the manual calculation, it is much lower than that....ie divide miles driven by gallons filled.

Am I missing something? Am I doing this wrong?

Thanks, any info or clarification would help me understand.

 

Don't know. Mine is accurate to about 1/2 MPG based on pump gallons and distance traveled.

 

Mine is off by about 1 mpg.

 

the computers seem to be about 1mpg higher than manual calcs. some are closer, some farther.

 

Mine is 1 mpg high. I wish there was some way(without a programmer) to adjust for this.

 

Discussed many times. It is accurate within 0.5 - 1.5 mpg and that's as good as it gets.

 

The computer calculations are fairly accurate since it measures metered fuel. Filling up and doing it the manual way leads to some error itself since there are a lot of variables--such as did you fill the tank to the exact same level as when you last filled it when you did the calculation. The only sure way to know it has been filled to the exact level is to fill it all the way up the neck and repeat it the next time. A 1/2 or 3/4 gallon difference calculating it the manual way can make a big difference. Assuming 400 mile tank if you put in 20 gals you get 20MPG but 19.25 makes it 20.77 which is with in the range of the computer accuracy.

 

That's what I've always figured. +/- 2mpg (approx. 10%) is within acceptable limits for me.

 

How does the F-150 calculate the amount of fuel used in order to show the miles/gallon? I have always thought it was not calculated but measured, but if the figures are not always correct then that can't be true.

 

The computer can easily calculate the amount of fuel delivered through the fuel injectors and it measures the distance traveled from the odometer and then calcs MPGs. Generally speaking the truck underestimates fuel consumption by about 8-10 percent. There is an easy way to adjust the fuel correction calcs if so interested to get the truck to display accuracy to 1-2%.