I went on a long drive to Wakefield a few days ago. My MPG on the trip computer was recorded as 72MPG.

Now when i finished my journey, 440miles later I filled up and worked out my MPG which came out as 53MPG.

Now I know the computer lies, but i sat on the motorway and didn't stop. almost 20MPG out is alot.

I was wondering if there is a way with VAGCOM to adjust its accuracy?

I found this:

Controller adjustment

STG 17 (combination instrument) select

STG adjustment - > function 10

- > channel 30 (tank fuel sensor adjustment)

The default value is 128, adjustable in 1 ohm steps (range 120 - 136).

But when I try to read channel 30 I get an error so I'm not sure this valid :/

Is that how the trip MPG calculation works then? Via the tank sensor?

I'm not sure, but I'm giving it a try. I have set it to 120ohm and have started on a full tank so I'll see what the real MPG is to the computer MPG. I'd be happy if it was only just 5MPG out.

There's a thread on how to do this - 'Useful VAG-COM Codes' or something. Depending on the age of your car, it may not be completely current, but it'll be a good start!

Then again, most people reckon about 10% out, so your readings are a bit extreme... :ne_nau:

I did have a look but couldn't see anything. The only other option is channel 03 for accuracy which you can modify (85% to 115%). Unfortunately this channel is non existent on my '06 VRS :/