Fuel economy figures

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Tue 27 Sep 2005 19:07
Fuel economy figures - Happy Blue!
This question has been nagging me for a while.

When the official fuel consumption figures are determined, I assume that they are done 'under laboratory conditions'. I further assume that they are carried indoors, on a rolling road.

Does this mean that the aerodynamic differences between cars counts for nothing, and that is why two different cars will get different figures in the real world, despite having similar offical figures?
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Espada III - well if you have a family and need a Lamborghini, what else do you drive?
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Tue 27 Sep 2005 19:27
Fuel economy figures - PhilW
"Does this mean that the aerodynamic differences between cars counts for nothing, and that is why two different cars will get different figures in the real world, despite having similar offical figures?"
I reckon so, because the figures for different cars with same engines are often identical eg Citroen C3 and brick, sorry, Berlingo seem to be identical with the 90bhp HDi engine (and probably Xsara?)
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Tue 27 Sep 2005 20:13
Fuel economy figures - Stuartli
The last time I was in a Ford showroom (about two years ago when my lad was buying a year-old Focus TDCI) I happened to spot the fuel consumption figures for all the 1.8-litre TDi and TDCI engines from 90bhp to 115bhp used in several Ford models.

The fuel consumption figures, to my surprise, were exactly the same no matter which engine was involved.
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Tue 27 Sep 2005 21:15
Fuel economy figures - Number_Cruncher
Estimates of aerodynamic drag among other corrections are added into the road load that the rolling road simulates - i.e., the rollers aren't free running.

Number_Cruncher
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