MPG readouts

[greendiff]

Over the last 9678 miles that i have done i have recorded my mpg figures manually, as well as noting down what the display tells me.

9678 miles, 46 fill ups, actual mpg from 12.3 to 32.7. display reads 14.4 to 26.1.

Now that doesnt seem too bad does it? Only a couple out.

But looking at individual figues, some extreme examples:

manual - car
12.3 - - 18.9
15.5 - - 23.9
32.7 - - 23.4
31.1 - - 19.6
13.9 - - 19.6
28.6 - - 15.2
16.1 - - 16.0

it seems to be display plus or minus anywhere up to 50%.

Just how do they get to be so innacurate, with modern injection systems, it should know what it puts in!

Edited by greendiff on Monday 10th March 13:28

[E65Ross]

That's ridiculous. I've done mine on 4-5 occasions and found the obc to read approx 5% out each time (it always reads better than you get, funnily enough!)

[TurboHatchback]

I've manually measured actual economy brim to brim on all the cars with mpg readouts I've owned. They have all been very consistent and fairly accurate, around 2-5% optimistic. I now take the display as read due to this.