Ok, so I start with a full tank. If I want to measure the mpg over several tanks, do I need to fill every tank all the way OR only the starting and last one?

Are there any links to describing best practices on this subject?

thanks,

 

Per tank, there is room for several % error. Average over
several tanks will be more accurate.

Use the same pump, stop at first click, to try to have a bit
more accurate per-tank numbers.

 

Miles traveled since last fill up = MPG
Gallons required to refill

 

MPG = miles driven / gas used.

1) Fill car up. Just fill up till the pump shuts itself off.
2) Reset tripmeter to 0.
3) Drive car till gas is pretty low, say till the low fuel warning light comes on.
4) Fill car up again. While filling, check your trip meter and divide the miles you drove by the gallons put in when you refill - that's your MPG for the last tank. Set the tipmeter back to 0.
5) Repeat for 10 or so tanks and you'll have a pretty good feel for your mpgs.

ps - It's best to run the gas pretty low to get a more accurate reading of what you put in when you fill up. Some gas pumps will shut off a bit sooner than others. If the tank is low when you fill up, this difference is minimized.

 

I never thought of that... but that makes perfect sense.

 

However, if you take an average of many tanks, this error will disappear. For one tank/measurement, that'll make it more accurate. however, if you do it through many averages, the margin of error disappears.

For example, if a fillup fills more than usual, that means the calculated mileage will be less. however, for your next tank, since you'll have more gasoline due to slight overfilling, your calculated mileage will be overestimated. Through many measurements, when you average it out, the inconsistencies of each individual fillup will cancel out.

 

Very true. As with most things, the more data points you have, the better

 

If you go to Gas Mileage Tracker - Software to track MPG on several cars. you can download a free program to help you track your mileage (MPG) and gas usage. I've been using it for three weeks and it's great for keeping track of what you spend, how much gas you've used, etc.

 

That looks like a neat spreadsheet to play with or use in a serious way.

Thanks for sharing it.

BigDozer66