Being anally retentive, I keep a regular check on mpg. The simple spreadsheet tells me mpg on this fill, average since the car was bought and, more usefully, average over the past ten fills. I think the latter gives a good idea of whether consumption is changing imperceptibly.
Figures have been remarkably stable at approx 34mpg except that a recent fill seemed to give only about 26 mpg. I'm satisfied that the record keeping is OK and that my driving pattern didn't change. Now back to normal.
Led me to wonder if there's any way the filling station could have fiddled me. Your thoughts welcome!
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I take it your spreadsheet doesn't take into account how you've driven on the tankful, atmospheric pressure, weather conditions etc, etc?
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I too keep spreadsheet details of my fuel consumption to check against my trip computer, sad aren't we, but it can vary quite considerably. My overall average is 31 mpg but fill-to-fill consumption can go as low as 26 when used for urban shopping trips and as high as 38 on mainly duel-carriageway trips, although we did get 43 mpg last year on a round trip Tamworth - Salisbury via M42, M40, A34, A30 at the legal limit.
Cold starts have a major effect on fuel consumption, even if the pattern is otherwise consistent.
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That's quite a wide variation.
Any chance that you filled with the wrong grade of fuel or the garage had got its fuel mixed (it does happen).
Was the running normal or at all rough or down on power?
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Have you got a locking fuel cap?
I knew a few who were dab hands with a can and rubber hose.
DVD.
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I once had a discussion at a filling station (attended) because the amount shown on the pump didn't tally with the volume delivered. Since the latter was more than the capacity of the car and the cash shown was even higher, we bargained a mutually acceptable sum to pay. Only happened once in 35 years though.
I used to keep a spreadsheet then the hard disk crashed and I thought "life's too short....."
Terry
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I keep the same sort of records. There's nothing surprising about a big fall or rise. Normally means that the tank wasn't full at the start or finish of the tank.
If the tank before or after had a high figure, that's probably all that has happened IMHO.
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If you follow the standard way of recording petrol/mileages, the tank full variations are dealt with:
Fill up tank, note mileage.
Next time, fill up tank again, note gallons added, note mileage.
Mileage between fills divided by fuel added = mpg.
As long as the tank fills to a clear cut-off point each time, ie it doesn't burble and splosh out, then surely this method is quite accurate, and gives a fill-by-fill record of constant or changing mpg?
I have kept records like this for years, although I have not graduated to spreadsheets yet. I have always found it a useful way of detecting things going out of adjustment or needing cleaning or changing, depending on the kind of car. Often a small drop in mpg indicates something needing attention long before it becomes apparent to the driver.
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Cliff
Don't pumps vary somewhat in the delivery flow rate? If they do & they seem to, then the cut-offs could vary, possibly being triggered earlier with higher flow-rates?
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Cliff:
Sorry to gang up on you, but will not pumps also vary in the sensitivity of the cut-off? I have had shoes covered in petrol more than once!
Andy
ps. I should learn shouldn't I!
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I have had shoes covered in petrol more than once! ps. I should learn shouldn't I!
CCTV on forecourts isn't there for security reasons. Your tape has been forwarded to You've Been Framed :o)
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No, I don't feel ganged-up on. I take your points. But with experience you get to know how full 'full' is with your car's filler, so avoid a shoefull. The point is not to fill it literally to the brim, but just to the same point each time, eg to the bend, first clip, filter, or whatever your car has.
I know pump gauges can't be perfect, but I am sure they are pretty accurate, good enough for this exercise anyway.
All I am saying is, if you can be bothered jotting down the details and doing the calculation each time, you do get a continuous indication of state of tune.
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I used a Metro as a pool car for several years and learnt to stand to one side when filling it as it vould invariably aim a dollop of petrol at your legs as it got to the top.
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Is that where the term "pool car" comes from?
Regards
Paul
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Nice to live somewhere where gas stations give you the service you're supposed to get, i.e. pert little gal who calls you sir, cleans your screen, checks your tires, oil, water then asks if she can do anything else for you. Or it could equally well be some pimply youth, but at least you don't have to do anything.
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