how to work out my mpg?

[almoststew1990]

How can I work out my mpg in an old car which doesn't have a mpg-o-meter?

Yes I know I can see how far I go on one tank and use my tank size to work out fuel per mile etc etc but I don't completely completely drain my tank, I overfill my tank and my tank probably has 19 years of crap resting in the bottom of it. Also my fuel gauge readings are rather unhelpfully not equally spaced- 3/4 full is more like 13/16 and a quarter full is more like 1/5

Anyone got any tips?

 

[snips86x]

Do you know how many litres or gallons your tank will hold?

 

[almoststew1990]

I know when it was new it was 50l.

 

[sovietspybob]

Fill car up at petrol station till the first click
Reset trip metre
Drive till fuel light comes on (or until fairly empty)
Fill up till the first click taking note of the litres used
Note down the miles you've covered from your trip metre

Put the distance you covered & the litres used into here http://www.mpg-calculator.co.uk/

You can use a website like Fuelly.com as i do so you can track a long term average as that takes some of the unpredictability out of a 'bad' fuel up where it clicks off early for example http://www.fuelly.com/driver/sovietspybob/yaris

 

[almoststew1990]

I forgot i get the actual fuel amount from the pump that was the missing info I need Boom thanks!

 

[lee1101]

This is great little free app for keeping track of your MPG for iOS. Requires input of the data mentioned above.

https://itunes.apple.com/gb/app/road-trip-mpg-mileage-fuel/id298398207?mt=8

 

[utajoker]

when empty fill up, look at pump and note litres and reset trip.

when empty put miles and litres into mpg calculator.

repeat get an average.

 

[xs2man]

http://www.fuelly.com/

I just keep the receipt, note the miles since last fuel up (I reset the counter every fuel up) and enter on the site. I also take a note of the OBC at time of reset, so I can compare OBC to real calculations.

 

[NeoVo]

Another vote for fuely, have been using for over a year now

https://www.fuelly.com/driver/neovo/astra

 

[xs2man]

Oh yeah, I could link my garage too, lol... 32,000 tracked miles since may 2012. I have missed quite a few receipts though...

http://www.fuelly.com/driver/xs2man/

 

[Scythe]

I know when it was new it was 50l.

Have you worked out what volume the tank can hold now? Tanks shrink with age, so any calculations you do now will be inaccurate

 

[xs2man]

Have you worked out what volume the tank can hold now? Tanks shrink with age, so any calculations you do now will be inaccurate

Surely the tank size is actually irrelevant to mpg calculations?

It's simply the miles driven for the fuel used, so as long as the tank is full at fill ups, it's simply the litres put in and the miles between fill ups? How big the tank is only determines how much you can squeeze in, and is unlikely to change very much at all between fill ups every 250 - 650 miles.

 

[Deleted member 66701]

Tanks shrink with age

Should I be checking the straps on this regularly if it's going to shrink?

 

[Scythe]

Surely the tank size is actually irrelevant to mpg calculations?

It's simply the miles driven for the fuel used, so as long as the tank is full at fill ups, it's simply the litres put in and the miles between fill ups? How big the tank is only determines how much you can squeeze in, and is unlikely to change very much at all between fill ups every 250 - 650 miles.

Wow clearly my comment went over people's head!

Yeah it is, generally for cars you'll know the tank capacity so you just see how much miles you've travelled to a tank. Or you can use how much you've filled off the petrol station receipt, and perform the same calculations as fuelly.