How to calculate mileage

[ill'n]

How do I calculate mileage? In my cage I would divide the amount to fill up the tank by the difference between current odometer and previous fill-up odometer. This was rather reliable because the amount of gas I pump in is usually 14 gallons, so small variations in fill-up amount won't affect the result too much. But on my Virago 250, each fill-up is only about 2 gallons. So if I'm off by even 1/4 gallon, my calculations are off by around 20mpg! Does anyone have any tips on how to better calculate mileage?

[jonnythan]

How do I calculate mileage? In my cage I would divide the amount to fill up the tank by the difference between current odometer and previous fill-up odometer. This was rather reliable because the amount of gas I pump in is usually 14 gallons, so small variations in fill-up amount won't affect the result too much. But on my Virago 250, each fill-up is only about 2 gallons. So if I'm off by even 1/4 gallon, my calculations are off by around 20mpg! Does anyone have any tips on how to better calculate mileage?

Do it over several fillups.

For instance, if you have the following data:

Code: Select all

Odometer    Gallons
42          1.6
40          1.4
55          1.9
45          1.7

Then add up the total miles and divide by the total gallons. This example gives you 27.6 mpg, but the single-fillup numbers range from 26.4 to 29 mpg.

[camthepyro]

You're over complicating it. Next time you go to the gas station, fill the tank up all the way, and set the tripometer to 0 (or write down what's on the odometer). Next time you fill up after that, write down how many gallons (exactly, to the decimal) it takes to fill it all the way up, and how many miles you rode since the last fill up.

Then just divide how many miles, by how many gallons. That's you mpg.

[qwerty]

Analyzing fuel efficiency calculations doesn't mean much if you only look at one tank. It's trends over time with type of usage factored in that indicate if something is wrong with the bike, if she likes a certain brand or octane, or if your most recent mode made any difference.

[camthepyro]

Well, how you're riding, where you're riding (hills or high elevation) make a big difference on gas mileage. But, if those calculations were done after regular riding (how you would normally ride) then that is a pretty accurate measure of your gas mileage for normal riding.

[ill'n]

Then add up the total miles and divide by the total gallons.

That's a fancy way of saying just take the average of my calculations over multiple fill-ups. Thanks, I'll do that. I'm sure the slightly more or less fueling levels when I top off will cancel out when averaged.

You're over complicating it. Next time you go to the gas station, fill the tank up all the way, and set the tripometer to 0 (or write down what's on the odometer). Next time you fill up after that, write down how many gallons (exactly, to the decimal) it takes to fill it all the way up, and how many miles you rode since the last fill up.

That's what I will do. Thanks. My problem was whenever I top-off, I'm supposed to stop at the bottom rim of that cylindrical tube that serves as the gas hole. But I can never get it exact, and I'm afraid it's throwing off my mileage calculations. Hopefully by averaging the numbers the errors will cancel out.

[jonnythan]

Then add up the total miles and divide by the total gallons.

That's a fancy way of saying just take the average of my calculations over multiple fill-ups.

Not technically, unless you're weighting the averages. Instead of averaging the final figures, you'd have to average the miles and gallons separately. That's going to be mathematically the same thing as doing totals.