Im with JJG052590, manual calculations can be done. As long as you fill your tank at every gassing and keep a record of how many gallons went in and a record of your odometer, you then just do the math. I also use this web site.

http://www.webwinder.com/ww_display_...ld_script_id=8

 

And neither are you!

 

I agree that manual calculations are farely accurate, but they are flawed. You have no way to know if you filled the tank to the exact same level every time. That is where the margin of error comes into play. If you keep a running total of fuel / miles traveled it will be much more accurate and get much closer to what the computer reads as MPG. I have an XLT so figuring the mileage manually is my only option. But I have had vehicles that figured it for me and I also kept track of the MPG's manually. After several tanks my manually calculated MPG's and vehicle calculated MPG's were within a couple of tenths of each other.

 

Good comeback!

 

It's not always going to be the same. For whatever that certain amount of miles are. You take the number of gallons you put in.. I HIGHLY doubt that it will be the same miles and gallons everytime! lol

 

In reading the owners manual I think it states something like "display calculates mpg/per every 100 miles and you should always reset everytime you reset your cruise for best results" I have done this in my truck and it does seem quite accurate! :o

 

Thank you, but I understand how to do the math. I never said it had to be the same mileage and the same amount of fuel each fill up. What I was saying is that if you keep track of the fuel pumped and miles driven over several tanks of fuel, the computer calcs and the manual calcs will get closer. That is because sometimes you may fill the tank a bit higher than the previous fill up and sometimes you may fill the tank a bit less than the previous fill up ( not amount of fuel pumped but amount of fuel in the tank after fill up ). Over several tanks the manually calculated avg and computer avg will become closer.

 

Oh okay I gotcha.. but I mean since we got XLT's that's our only option!

 

I agree, and I believe I said that was how I did it. However, if you keep a running log of your avg MPG's over several tanks and then avg them together, you will get a more accurate MPG figure than off of just one tank. When I avg my MPG's on just 1 tank I get a range of anywhere from 14.6 to 16.1 MPG. But after keeping track over several months, my avg is about 15.5 MPG.

 

And there have been many NASCAR teams that have run out of fuel w/4 laps to go...figure they were on a (average) 2 mile oval...that's 8 miles...almost 1/2 gallon (or more), according to some MPG estimates I've seen here...plus, they do thier calculations on weight, not volume...one other thing, you are trusting the number on the fuel pump (gallons pumped) as being accurate...I wouldn't, unless you use the same pump on the same day...within a few hours..

But, as was said before...use whatever method makes you happy..

R/
Craig

 

Either way you do it, there shouldn't be a 2-3 mile difference! I'd go the manual way. Write down your average for the next 10 fill-ups, then you'll have a good average!

 

I'd still take the computers average...it (the computer) does not take egos into consideration...Did I pump 20 or 20.897 gallons?? Do I have 300 miles or 282 miles on my odometer??

If you are at the same pump at the same station, does the cut off happen at the same back pressure...or does it happen 1/2 to 1 gallon sooner or later???

My daily driver is a VW Golf TDI, I get, by my meager calculations, 50-54 MPG...however, I can also fill the overflow up to 1 gallon over what the rated capacity of the tank is...does this make make manual calculation correct?? Not if I fill the overflow to capacity, then drive 700miles, then fill until the nozzle clicks off..

I believe that the actual MPG will be between the manually measured MPG and the computed MPG...they are both guesstimations..

R/
Craig

 

[QUOTE=26point2]I'd still take the computers average...it (the computer) does not take egos into consideration...Did I pump 20 or 20.897 gallons?? Do I have 300 miles or 282 miles on my odometer??

If you are at the same pump at the same station, does the cut off happen at the same back pressure...or does it happen 1/2 to 1 gallon sooner or later.


Does it matter when the pump shuts off? It shouldn't! If you can't write down the correct gallons then you should use the computer. When I fill up I always get the receipt and write down the mileage to the 10th and also the trip mileage. The gallons pumped is always on the receipt. Then I enter it into my computer at home and it's done. After the auto shut off on the pump kicks off I always wait a cpl seconds then pump again till it shuts off again and I'm thru. To figure fuel mileage you don't "have" to know the size of the tank, just the gallons pumped and the mileage.

 

I am using the longhand calculation. When I griped about the crappy mpg's at the dealer they asked wether I was calculating or trusting the computer. They indicated that the computer wasn't accurate.

My 05 is getting about 11/11. I have seen as low as 9 mpg and as high as 14, but all in all I see 11. The computer usually is within about .5 mpg of my calculations.

Regards!

 

I drive till my buzzer goes off and then I stop and put the same amount in; $20.00. If I do this for three or four times at the same price, then I just divide the miles driven by the number on gallons I used each time and there it is, as simple as that. I've been averaging around 20 highway and 17 city here lately.