Just wondered how you fellow owner drivers work out the mpg for your vehicles. Do you just go by what the computer says or do you work it out by diesel fill ups? Which do you believe to be the most accurate way of doing this?
Cheers
Matt.
Always use mileage between fill-ups and litres brim to brim: it’s the only way. Never had an on-board computer be 100% accurate.
Then if you want to get clever, you can use Excel to manage this.
I can build you a workbook to do this if you would like
Brim the tank each time matt on the same pump each day if pos ,do kilometres times .62 to get the miles and litres divided by 4.54 to get the gallons it’s by far the most accurate way.
nvHerman:
Always use mileage between fill-ups and litres brim to brim: it’s the only way. Never had an on-board computer be 100% accurate.Then if you want to get clever, you can use Excel to manage this.
I can build you a workbook to do this if you would like
Bloody hell that sounds far too technical for me!! So basically brim the tank on say a Monday, write down the mileage and then brim the rankin a Friday but don’t take that fill up into consideration? Is it better to do it over a week period or monthly?
xfmatt:
nvHerman:
Always use mileage between fill-ups and litres brim to brim: it’s the only way. Never had an on-board computer be 100% accurate.Then if you want to get clever, you can use Excel to manage this.
I can build you a workbook to do this if you would like
Bloody hell that sounds far too technical for me!! So basically brim the tank on say a Monday, write down the mileage and then brim the rankin a Friday but don’t take that fill up into consideration? Is it better to do it over a week period or monthly?
That’s up to you, I personally would just calculate every tank full used.
xfmatt:
Bloody hell that sounds far too technical for me!! So basically brim the tank on say a Monday, write down the mileage and then brim the rankin a Friday but don’t take that fill up into consideration? Is it better to do it over a week period or monthly?
Its easier just to brim the tank each time, although you don’t have to.
E.g.
Monday - Brim Tank (note mileage)
Wednesday - Brim Tank (put in 300 litres) ***you don’t have to calculate mpg here but you could do if you want.
Friday - Brim Tank (put in 250litres) Note milage
Say you’ve covered 1,750kms.
To get miles x0.6213 = 1087.3miles
You’ve put in 550litres.
To get gallons divide by 4.543 = 121.1gallons
Divide your miles by your gallons.
1087.3/121.1 = 8.98mpg
As long as you note the mileage at the beginning and at the end of the period and include ALL fuel added during that time you can accurately calculate your MPG.
Once you know your MPG you can calculate how much its costing per mile or km…but that’s another story! 
Have been comparing truck computer with brim to brim and fuel bills for year to date, computer is spot on, some may better than others though.
With the company I’m working for we tell them the start/end milage, fuel put in and if it’s put in in the yard then the diesel pump wants milage (even the red diesel pump wants milage, but it also goes on the unit’s account.
We can use the onboard computer to get mpg and they like us to get about 9mpg and keep the revs below 1500rpm
Wow they want 9mpg & You to keep it under 1500 rpm, I can see that bit but 9’s at full weights I doubt it very much…
I never took a blind bit of notice on what the dashboard told Me, quite simply it lies like a cheap watch.
Tankfull to tankfull doesnt really give You a true average IMHO but week to week or better still monthly does. 4.546 & 1.6093 & you wont go wrong.
Flysheet; that’s an average for the day. So when running empty, which for me is half the trip, I can get a fair bit but when loaded it drops a fair bit, but it’s all about considerate driving isn’t it.
My only drawback I can see is putting my foot down to pull out of junctions lol
Nice & simple conversion factor as everything is measured in km & litres.
Km divided by litres multiplied by 2.825 gives mpg
If you have a smartphone, search for the FuelLog app. Lets you choose your own parameters (miles, kilometers, gallons, litres, etc.)
Every time you fill up just fill in the boxes and it does the rest for you. It will also tell you your average, best and worst fuel consumption figures.
You can keep track of more than one vehicle with it. And you can use it to keep track of other vehicle costs.
Really easy to set up and use too.
For a quick conversion to MPG, divide kms by litres then times by 2.825.
Dan Punchard:
Brim the tank each time matt on the same pump each day if pos ,do kilometres times .62 to get the miles and litres divided by 4.54 to get the gallons it’s by far the most accurate way.
This.
If you want to be really ■■■■:
4.546 ltrs per gallon.
1.62 kms per mile.
(When pricing jobs for customers i use a local Shell garage as a point of reference for the customer to establish fuel prices then, depending on the job quote at 8mpg).
There’s a US based website called mygauges.com you can sign up and it will track your mpg for you, it has the US gallon and the mile as standard but you can change it to litres and kilometres.
It gives you a lifetime/90 day/60 day/30 day and weekly average and is very easy to use. It also gives you a cost per mile, but obviously being a US site that will be in cents per mile, you will have to pretend you have a Peterbilt or a Kenworth as they use yank tanks, but you’re in luck if you have a Volvo 
It’s worth a look, if you can get registered it’s a lot easier than poncing around with excel spreadsheets
I’ve been using fuel buddy available on the android apps , set up everything to work out mpg by putting km’s and litres in , put the app on your phone or tablet it helps me moniter the obvious , I know when fuel filter are due for a change for example as mpg dips slightly the other week it helped diagnose a sticking trailer caliper ( I knew anyway but it helped back me up) and the figures match the company computer that is linked to the fuel pump , the truck mpg computer figures are normally .75 - 1mpg worst than true figures suggest.