What was my mpg ??

xcessive · 2 Oct 2006 at 19:28

Hi

I want to work out my mpg for a rather large journey i went on yesterday.

I drove 404 miles
Filled up twice, the first time i filled up with £27 and the second time i filled up with £19.50.

At both times the petrol cost 84.9 pence.

I did motorway driving (trekking up and down the M1).

When i left my house i had quarter of a tank of petrol and when i returned i had the same.

I've tried some of those online mpg calculators but they say i've been doing 47 miles to the gallon which can't be true because according to my owners manual it does 35mpg!

Thanks

Del Lardo · 2 Oct 2006 at 19:30

33.5mpg

27+19.5=£46.50/0.849=54.77litres*0.22=12.05gallons

404miles/12.05gallons=33.53mpg

MrMatteh · 2 Oct 2006 at 19:32

I work it out as 33MPG

[TW]Fox · 2 Oct 2006 at 19:34

Ignore all these figures as they are inaccurate. You cannot accurate calculate fuel consumption by saying you had a quarter of a tank when you left and a quarter when you got there - your fuel guage is not a calibrated instruement and is notoriously inaccuate.

The way to do it is to brim the tank, reset the trip counter, drive, then brim the tank again. This will then tell you exactly how much fuel was used to cover the distance you covered.

xcessive · 2 Oct 2006 at 20:06

[TW]Fox said:
Ignore all these figures as they are inaccurate. You cannot accurate calculate fuel consumption by saying you had a quarter of a tank when you left and a quarter when you got there - your fuel guage is not a calibrated instruement and is notoriously inaccuate.

The way to do it is to brim the tank, reset the trip counter, drive, then brim the tank again. This will then tell you exactly how much fuel was used to cover the distance you covered.

I know that it wont be 100% accurate but surely a fuel gauge cant be far off.

With the 33mpg fuel consumption im very happy. I'm sure i was probably getting around 30mpg (taking into account what fox has said) because i wasnt exactly driving in a fuel efficient fashion!

Jonnycoupe · 2 Oct 2006 at 20:07

Your assuming here that the odometer is bang on too. Its very unlikely

xcessive · 2 Oct 2006 at 20:07

Del Lardo said:
33.5mpg

27+19.5=£46.50/0.849=54.77litres*0.22=12.05gallons

404miles/12.05gallons=33.53mpg

I thought i was 4.54 miles to a gallon :confused:

(i may be getting imperial and US gallons mixed up though

)

xcessive · 2 Oct 2006 at 20:10

To avoid confusion here i am not asking for an exact figure for my fuel consumption.

Just a rough sort of estimation so i know roughly how many miles per gallon i was doing.

I know the fuel gauge isnt 100% accurate but it can't be THAT far off. Or can they??

Tomsk · 2 Oct 2006 at 20:47

xcessive said:
I know the fuel gauge isnt 100% accurate but it can't be THAT far off. Or can they??

Yes. If I believed my fuel gauge I could drive 500 miles, whereas in reality I would be lucky to travel 400

Fr0dders · 2 Oct 2006 at 21:45

the number of times my trip computer has told me i have 0 miles remaining is quite humerous !

but admittedly i would probably only get another 10 miles or so max out of the tank at this point, being on the last bar of the electronic fuel guage.

austinpowers · 2 Oct 2006 at 22:39

I make it roughly 33.53 mpg.

£27+£19.50 = £46.50

£46.50/.849 = 54.77 litres

404 miles/54.77 = 7.37 litres x 4.54 (uk gallon) = 33.53

But yeah you need to brim the tank drive for a couple hundred miles then brim again.