Hey,

So I am wondering how exactly does the trip comp calculate your average mpg? And secondly, how accurate or otherwise is it? Mine averages 35mpg (normally asp 1.8) which seems reasonable.....

Every 5 seconds it records the current readout on your "instant" mpg gauge, then puts all these in a big table and divides them by the total number of recordings it's made so far to get the average mpg.

That's why when you reset the gauges the average will vary wildly to start off with as you are doing all sorts of speeds, but after a good hour or so of driving it will settle down to a reasonable figure and only change slightly every so often.

Mines currently averaging 34.4 mpg, combined town and motorway driving.

I've read before on here that the mpg is about 5% out, so a 35 mpg reading is actually more like 33.2 mpg. You can reset it using VAG COM to make it more accurate.

The trip and o/a average figures can be as much as 10% optomistic; bizzarely the "available range" one is pretty accurate as long as you don't expect decent data in stop-start or the first 10mins from a cold start.

35mpg seems a bit low as I used to get around 32-35mpg out of my Mk 1 VRS (on a long run could get close to 40mpg).