MPG Calculator.

[Grant123]

i have a new C220 CDI C204, its new so has less than 500miles on it so far.

i did a reset on the computer when i filled it up, currently the onboard computer says i'm averaging 37.7mpg over the last 300miles of driving.

Using a web mpg calculator, its saying i'm averaging 47.05MPG.
>> Fuel Calculators » Fuel-Economy.co.uk

seems quite far out, anyone got an idea of,
a. whether the accuracy will improve with time
b. or could it be using US Gallons? as 47.05 uk MPG = 39.1 us mpg




thanks

 

[Sp!ke]

How many miles did you do and how many litres did you need to fill up with?

 

[Frugal]

There seems to be a wide variation in accuracy of the onboard MPG meter but yours does appear well out and pessimistic too. Mine has been steadily 7% optimistic from new 18months ago. May be worth mentioning to your dealer.

 

[Grant123]

£40 & 139.99p per Litre (28.59L)
300 Miles.

I think its displaying US Gallons, as the onboard MPG Graph on the command system NEVER goes above 50mpg even if i sat at 60-65mpg on the motorway,

Do you know how i can access this using the Onboard settings to check?

 

[Sp!ke]

your calculations are correct

6.35 imperial gallons into 300 miles is 47. Can you change your display to Litres/100KM?

 

[Grant123]

I'm not sure, i cannot seem to find a option within the setup menu.

 

[Sp!ke]

Guessing you have checked your owners manual?

 

[Grant123]

i have, its full of useful info.

i suppose it doesnt really matter so much as the daily MPG calculations seem correct, just appears it doesn't calculate well over long distances/days.