Real mpg

[MMM]

The only way to get ir right is topping up and then after 1,000 miles or so of jotting down amount of fuel purchased top again and make the calculation.

Based on this I found myself getting an average of 43.1 REAL MPG hilly terrain, doing some hypermiling.

The dashboard AVG is off by 12/14%

MMM

[mr_z]

Originally Posted by MMM

The only way to get ir right is topping up and then after 1,000 miles or so of jotting down amount of fuel purchased top again and make the calculation.

Based on this I found myself getting an average of 43.1 REAL MPG hilly terrain, doing some hypermiling.

The dashboard AVG is off by 12/14%

MMM

That makes sense really. Just check your odometer, save your receipts for a few months, check the number on the odometer when you just about run out on the last tank. Then divide. It's probably the most reliable method. I plan on doing this after the break-in period.

[secondspassed]

Yeah, sounds more reliable but a little overkill. I calculate my mileage on almost every tank when I fill up by simply dividing the miles I've driven since last fill-up by the amount of gas the car took. I know this isn't accurate as a one-time calculation but my results end up being so close together and regular that I know for sure I average 33-34mpg in my '08 AT Fit.

[wdb]

The big problem with per-fillup calculations on the Fit is its wonderful "magic" gas tank that supposedly holds 10.9 gallons but into which people like me routinely pump 12+ gallons.

I can usually get an additional 2 gallons in the car after the pump kicks off the first time. With that much additional space in the tank, the pump's kick off point becomes a critical factor in determining how much fuel goes in, and hence the miles per gallon you will calculate. Averaging over multiple tankfuls helps smooth that out, if you choose not to 'hyperfill' the tank each time.

[secondspassed]

My view is that the "magic" gas tank factor only ever affects an individual result and since I *only* give a damn about the long term averages I don't sweat it. I guess we're pretty much saying the same thing.

EDIT: If I were trying to be able to say I had achieved a certain high mileage on any given tank (like many on FitFreak) I would probably change the way I calculate my mpgs. :P