Official MPG Figures Unrealistic, Says UK Auto Magazine 238
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."
Re:What's that in KPL? (Score:5, Informative)
Re:Real-world conditions (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. [carconsultantni.com] 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.
Re:Real-world conditions (Score:5, Informative)
This story is about European standards which are a bit wacky, but I know they get spot-checked in the US. Hyundai paid out a huge settlement for (apparently honestly) screwing up the testing.
Remember that your competitors are probably testing your cars, too :)
Re:Which is why sometimes small engines ... (Score:4, Informative)
Re:Real-world conditions (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.
Re:Real-world conditions (Score:4, Informative)
That's the key here. EU mileage figures are rated based on the NEDC cycle [5-stroke-engine.com], which gives about 15% better mileage figures than the EPA combined cycle. Given that this guy is saying real world is 19% worse than the NEDC, then that's a pretty good testament to the EPA combined cycle.
At least the NEDC is better than the laughable Japanese 10-15 cycle [epa.gov], which gives figures about 10-15% even better than the NEDC.
It's one thing that drives me crazy when Americans point out to cars overseas and say, "Look, how come they get cars that are so much better mileage than ours?" The truth is, there's not actually all that much difference. UK car figures are often even worse because they're usually reported in miles per imperial gallon, which gives an extra 20% boost to mpg figures. On top of that, a large percent of European cars are diesels. While it's fair to compare diesels to gasoline cars when comparing what ou have to pay for fuel, it's not so for an environmental comparison. Diesel is 10-15% denser than gasoline; a gallon of diesel represents 10-15% more oil consumption and emits roughly correspondingly more CO2 than a gallon of gasoline. If one cares about CO2, the best approach is to ignore MPG and look at g/100km figures, which are almost always based on the same cycle (NEDC) and take into account differences in the fuel.