MSE News: Government miles-per-gallon car figures 'unreliable'

edited 30 November -1 at 1:00AM in Motoring
67 replies 6.2K views


  • Trebor16Trebor16 Forumite
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    Strider590 wrote: »
    They are of course idiots anyway, if they think buying a new car can save them money at all.... Even if the old one did 35mpg and the new one 50mpg.

    Why are they idiots? If they need to replace their car because the existing one is no longer reliable how does that make them idiots for choosing to buy something more fuel efficient?
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    John539 2-12-14 Post 15030
  • Trebor16Trebor16 Forumite
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    So why do I regularly exceed them?

    Perhaps because you are being economical with the truth with your claims?:D
    "You should know not to believe everything in media & polls by now !"

    John539 2-12-14 Post 15030
  • Maybe it didn't give a link because the list of makes is incomplete? :)

    I just tried it and it doesn't list Vauxhall, which is what I drive, as a make. Seeing that What Car advertises itself as "Britain's biggest and best car buyer's guide" I'd say this is pretty disappointing.
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  • Mary_TaMary_Ta Forumite
    9 Posts
    The best website for realworld mpg is the German "www dot spritmonitor dot de slash en" website. As they claim on their front page it contains data for over 300,000 vehicles and 4.6 billion miles of motoring. Its calculated for each user on a tank to tank basis, you can search by vehicle type, fuel type etc. and it provides barcharts of consumption distributions, averages etc. - you can then drill down to look at consumption patterns on individual cars. If you can't cope with l/100km, either divide the number into 282, find a conversion website or setup a login to the site. It is likely to be more accurate than wither whatcars site or honestjohn's equivalent.
  • Kite2010Kite2010 Forumite
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    Why in this day and age isn't fuel economy figures quoted in Miles per Litre and not Miles per Gallon, after all fuel hasn't been sold in Gallons for ages.
  • UltrasonicUltrasonic Forumite
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    What always confuses me about the standardised mpg tests is that they don't appear to include the effect of wind resistance, do they? If not then from the point of view of these figures it is a waste of time manufacturers making their cars more aerodynamic. This would also guarantee that real world fuel economy figures are lower.

    The What Car test is of very little value though. Whether or not they give exactly representative figures, the whole point of the standardised test is that they let you compare cars on an equal footing. Asking a test driver to try and drive in roughly the same way repeatedly is bound to be innacurate. Ideally I'd want to know what fuel economy I could get with my driving style, but as this is impossible I'd rather stick to the standard test results thanks.

    For what it's worth the average mpg I've had in my last two cars is very close to the manufacturer's quoted combined mpg figures.
  • patman99patman99 Forumite
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    Before I bought my X-reg Octavia 1.9Td I researched info about the expected mpg on the web and the average seemed to be 58mpg. as this was 20mpg better than I was achieving with my S-reg Focus 1.8 Zetec, I took the plunge an bought it.
    So far, I am averaging 71mpg+. Filled-up with £50 of BP Ultimate and reset my tripmeter. So far have only used two segments worth of fuel and have completed 245 miles.

    My driving is a mix of motorway and A roads.
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  • UltrasonicUltrasonic Forumite
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    patman99 wrote: »
    So far, I am averaging 71mpg+.

    I really hope that is genuine, but I fear it may not be. I have a 2005 Octavia 1.9TDI and the fuel economy indicated on the trip computer is about 10 mpg over optimistic (as checked with the old fashioned brim to brim method). For info I try hard to drive economically and the best economy I've managed on a tank is in the low 60s mpg.
  • CKhalvashiCKhalvashi Forumite
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    I’ve always got between 30-35% less than the official MPG (although it’s possibly due to the car normally being on kick-down during acceleration).

    Cars are tested under perfect conditions, and the only time I am exceeding the ‘target’ MPG is on the 90mph daily commute (where the car’s constantly in 6th gear on cruise control).

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  • UltrasonicUltrasonic Forumite
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    Eighth Anniversary Combo Breaker
    CKhalvashi wrote: »
    ...the only time I am exceeding the ‘target’ MPG is on the 90mph daily commute (where the car’s constantly in 6th gear on cruise control).

    You'd exceed it a hell of a lot more if you drove at 70 mph... (The air resistance at 90 mph is huge, and to be honest I'm astonished you're exceeding any quoted efficiency at that speed.)
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