MPG innacurate on OBC

[IPityTheFool]

Intrigued by the fact that my 200 was getting around 400 miles between fills yet the OBC was saying 32-34mpg approx on average for each tank, this didn't add up so i have measured a few tanks!

Last tank:
Miles covered before refill: 378
Litres(Gallons) at refill: 47(10.44)
MPG: 36.1

OBC Litres consumed: 51.75
OBC MPG: 32.0(doesn't even tally with gallons consumed and mileage???)

Not noted down the other tanks but i did one tank where the OBC showed just over 30 average and actual average was 34. Did one tank with OBC showing around 36, actual average was 39ish.

Seems that the computer is showing a lower MPG than actually acheived? And is showing more fuel consumed than has actually been used, i thought that it worked on injector duration and rpm so could calculate how much had been used. The trophy one was pretty damn accurate, usually calculating fuel consumed to within 0.1 gallons of the measured amount and mpg was essentially spot on!

What have you found?

 

[Ed...]

is that until it ran out? i found when i was filling mine to the brim it wud take about £65 but never used it untill it ran out.

also i think the tempertaure can effect mpg

+ it wont do the last 50 miles so will never be 100% accurate.

 

[IPityTheFool]

Nope not until it ran out, usually refill around when the light comes on. Do 800 miles a week approx so 2 fills a week. Was considering selling due to bad economy but it's actually pretty good i think!

 

[Ed...]

yeah u do the same miles as i do. if ure on motorways its fine its city driving when the MPG is poo

 

[RalphyBMW]

Woody your first post doesn't make any sense. This guy is talking about the OBC reading Vs actual, not the cars economy in general.

Mine is typically about 10% out, not compared the fuel used on the computer, but the MPG is typically around 10% out. If you are registered on spritmonitor.de you can see my actual consumption plus the info from the OBC in the notes.

 

[Ed...]

y would it matter?

 

[Ed...]

The OBC is just a rough guide wudnt take it as gospel it only updates itself for the first 100 miles or so

 

[Roy]

dont bother with that mph thing any more
just depresses me thinking how much i used to spend
but its a 197 and it drinks fuel
rant over :-p

 

[Ed...]

yeah performance car didnt buy it to save fuel lol thanks roy

 

[MikeLYR27]

Thats to eco friendly start seeing the shift light lol!

 

[Paul]

TBH Im quie happy if it says 30mpg and you actually get 35mpg, means my 27.5 might be above 30 lol! I would only be annoyed if it was over-estimating badly. At the end of the day if you drive the nuts off a Prius it wil only do 19mpg lol!

Its not what you drive its how you drive it - FAST! :-p

 

[quik97]

mine currently says 21mpg and have never seen over 25 so god knows how your in the 30's.

 

[richandgem]

If ur mpg is over 30 your not doing it right guys, press the loud pedal a bit harder

 

[jaxx]

If ur mpg is over 30 your not doing it right guys, press the loud pedal a bit harder

Good call :clap: