Date: 1 May 2004 13:31:50 GMT From: Dave Hinz <davehinznospamcop.net> Subject: Re: Fuel consumption figures computer wrong
On Sat, 01 May 2004 09:27:46 +0100, Colin Stamp <colinnospamp.plus.com> wrote: > On Sat, 1 May 2004 07:56:41 +0100, David Taylor <djtaylornospamoot.com> > wrote: > >>Nothing wrong with doing that except that a) you don't know the accuracy >>of the pump and b) can't guarantee that the fuel cut off works exactly >>the same the next time so discrepancies in the filling aren't being >>taken into account. > > Pumps should be reasonably reliable - I'm pretty sure they are legally > regulated. For volume, yes. But switching off when they feel the tank is full? Probably not, which is what I think David was getting at. > It won't be perfect, but you'd have to be going some to get > it wrong by over 6 litres in a tankful. Adding up all the > uncertainties I'd expect well under 5%. It's watched in the US, but people have been busted for it. Couple of years ago, one of those investagative TV programs found that some stations in large urban areas were playing with the numbers on the pumps, which was of course followed by industry people saying it can't be done ;) > For as much as 10%, I'd be starting to worry that something was wrong > - maybe the fuel rail pressure is a bit high or something. Tire diameter maybe? If the tires are significantly different than what the car shipped with, that'll throw the distance part of the equation off as well. If it's a, say, 7% error, that's a lot when it comes to fuel, not so much when it comes to tires. A GPS could be used to measure overall distance, if it's all within view of the sky. Dave Hinz
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