Acuracy of on board computer

[daveyonthemove]

Filled up today, and out of boredom and slight interest i decided to compare the On board computers result on overall MPG for the last tank to an actual working out of the MPG.
It was only over 215 miles so not a huge distance in order for the results to vary, but even so i go the following.
OBC 41.1 MPG
Actual 41.8 MPG

Not too far out, so i'll see how it looks after a full tank full is used.

 

[CHR15B]

I worked mines over a full tank the results are similar to yours, infact nearly bang on.

OBC : 53.2 MPG
Actual : 53.9 MPG

My Dad also done the same test on his Audi A6 2.5 TDI and found that the OBC/Actual were both in the 29MPG mark.

 

[Husbandofstinky]

Last time I did it, it was pretty accurate. Haven't got too excited about it as things seem about the same since.

Interestingly the computer seems to like the recent stage 2 remap and appears to be running a mile or so per gallon more economically.

Wll do a proper check on it soon when I remember.

 

[craig-pd130]

I checked mine over a couple of tankfuls a while back, it was 4.5% optimistic, which is still pretty close to the truth, anything over 52mpg on the computer is a real 50mpg

 

[glynnd]

Before my remap mine was about 5% over reading.
Sice the remap its almost 100 accurate
Glynn