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Official MPG Figures Unrealistic, Says UK Auto Magazine

Posted by timothy on from the your-mileage-may-vary dept.

Taco Cowboy (5327) writes "Research carried out by UK consumer magazine What Car? which concluded that official manufacturers' MPG figures are unrealistic. Based on the research, new car buyers in the UK who trust official, government-sanctioned fuel economy figures will pay an average of £1,000 (€1,216) more than they expect on fuel over a three-year period. Since launching True MPG two years ago, What Car? has tested almost 400 cars in real-world conditions, using cutting-edge test equipment and achieving economy figures that are on average 19% lower than the government figures."

5 of 238 comments (clear)

  1. Real-world conditions by Anonymous Coward · · Score: 5, Insightful

    Under-inflated tires, lousy fuel, ignored maintenance, rapid acceleration, more than one occupant / actual cargo, stop-and-go traffic, air pollution, air pressure variation, air temperature variation, elevation variation...

    And these are just a few of the things that would cause your "official" MPG figures to deviate from observations.

    1. Re:Real-world conditions by Chrisq · · Score: 5, Informative

      Under-inflated tires, lousy fuel, ignored maintenance, rapid acceleration, more than one occupant / actual cargo, stop-and-go traffic, air pollution, air pressure variation, air temperature variation, elevation variation...

      And these are just a few of the things that would cause your "official" MPG figures to deviate from observations.

      That's all true, but manufacturers go to great lengths to inflate the figure. They disconnect the alternator, tape up cracks in the bodywork to improve airflow, remove wing mirrors(!), disconnect the brakes to reduce friction and use special oils in the engine to improve efficiency. Figures are not just a bit off but way off. My car has an official figure of 68.9mpg. On a good trip, driving on a flat road at about 70 mph I can get 54, but my usual average is 35 mpg. This is with gentle driving, I can easily take it down to 25 if I don't take care.

    2. Re:Real-world conditions by KozmoStevnNaut · · Score: 5, Informative

      Also set up wrong by the manufacturer. The 2007 honda civic has a highway MPG rating of 40mpg. I regularly get 44-46 while speeding after I fixed their design flaw in the rear end. they set the car with significant negative rear camber and with about 2 degrees of toe, I reset it to zero and zero and not only did fuel mileage numbers skyrocket by 10-15% but rear tire wear dropped to zero or undetectable. From what I can tell they STILL sell civics with this flaw, and the Honda Fit as well suffers from it.

      That's not a flaw, it's a deliberate design to improve stability and handling, especially during mid-corner corrections and emergency maneuvers. The slight toe-in also helps straight line stability.

      My car (Peugeot 406) is setup like that as well, it has enough negative rear camber that it is immediately noticeable when looking at the car. If you try to "correct" this by dialing out the camber, the car will be less stable over mid-corner bumps, and the small amount of passive rear steering built in the rear suspension will be negated, further worsening the handling.

      What you have done is make your car go from being relatively neutral in corners, to having positive camber when the suspension is loaded up. If you've ever read "Unsafe at any speed" or seen an old VW Beetle corner hard, you will know that having positive camber is one of the most dangerous situations you can be in. So you've actually made your car significantly less safe, all for the sake of a few MPG. Congratulations, I hope you're proud.

      --
      Eat the rich.
  2. No fuel economy figures are going be right by Anonymous Coward · · Score: 5, Insightful

    Isn't the more important thing that the all the cars figures are comparable.

  3. Re:watch the program on 5th gear by rolfwind · · Score: 5, Funny

    and it was designed i think well over 20 possibly even 30 years ago. so it has a very *very* gentle acceleration and deceleration curve. gentle acceleration because that is not only fuel-efficient but also the cars of that time simply could not accelerate that much...

    WTF are you blabbering on about? Cars from 1980 or 1990 could not accelerate that much?

    You must be a young kid or something, but not everything before your time was primitive by virtue of you not having come along yet.