I applaud your efforts to record achieved MPG figures against the manufacturers' quoted numbers at www.honestjohn.co.uk/realmpg. The mpg readout on my BMW 318 computer is consistently four to five mpg more optimistic than the fill-to-fill calculation. I have checked my odometer regularly (over 40 to 50 mile distances where possible) against roadside markers and it is very accurate. As a result I am sceptical about the numbers quoted by your correspondents from time to time - sometimes qualified as being from a single round trip.

In loading your database, are you able to differentiate between calculated fill-to-fill mpg and computer readouts and identify distances and driving mix urban/long distance? Depending on my driving mix over 104,000 miles I can get calculated averages, full tank to full tank, ranging from around 30 to over 50 mpg, with the computer always four or five mpg optimistic. With many reports it may be possible to get a reasonable average to compare with the official figures, but some qualification of the basis of individual reports would really add credibility to the database. Good luck with your efforts.