Originally Posted by
wai
The thing is that the published fuel consumption figures are run in accordance with a standard. This makes sure that the conditions and cycle that one vehicle operates will be exactly the same as another vehicle. As such, the figures can only ever be used for comparative purposes, and even here for the same type of vehicle only (i.e. passenger cars or wagons or vans)
Fuel consumption calculated in everyday use can vary tremendously because of the number of variables like wind (speed and direction), temperature, tyre pressure, road surface, traffic, a/c use, windows up/down, etc.
By the way, this is also why there is no correlation between official test emissions and emissions measured using a on-standard drive cycle that has not undergone any verification process.
It's the same test. They don't run a separate test for fuel consumption. While testing emissions they measure what comes out of the exhaust pipe - with modern white-man magic, they derive from the exhaust how much fuel was burnt.
As with emissions, it's not intended to be the ultimate guide to real-world results. It's supposed to be a standardised test that allows comparative assessment - how does any particular model compare against other vehicles under the same (artificial) conditions.
In the test lab, employ emission controls, have "clean" exhaust but burn more fuel.
In the real world, ignore emission controls, have "dirty" exhaust but burn less fuel.
Former owner of MY12 GTD with DSG
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