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      11-23-2012, 10:07 AM   #24
HighlandPete
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Drives: BMW F11 535i Touring
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Quote:
Originally Posted by sfax View Post
I think people would be much happier if the advertised combined mpg was about 45. It's the realms of fantasy that produce figures of 56mpg extra urban that should be reviewed as they are misleading. I think it's a combination of BMW using a certain optimum setup (17" low rolling resistance tyres for example) for the test car and the test cycle itself not really being anything like real driving patterns
If the official figures were more realistic, then there would be massive implications for CO2 targets across Europe. Current tax on emissions (BIK) would be much more expensive. So in one way there is not much will to sort this issue out.

The other issue, I sense the extra-urban figure is the one car sales and users are enticed by, "the car can do up to ---mpg", all sounds impressive but in reality, when has it had any serious part in judging real world economy?

Even the combined figure is a misleading figure, as it means nothing to most users, it isn't reflective of any particular driving mode, not even something like motorway driving. Not many cars will even give the combined figure at 70mph, more like 60mph as a rule of thumb, for an average sized car with average size engine. But again so many variables, which means something like a Smart Fortwo with a combined figure of 85.6mpg will return 48.5mpg at 70mph. Whereas a BMW 520d saloon will be over 50mpg at 70mph, just 5mpg below its combined figure. But something like a Ford Focus ST will return several mpg more at 70mph, than the official combined figure.

But unless you really understand all the smaller details of what makes a fuel efficient model, the official figures are all we have to compare with.

When we factor in the official tests will be on base specification of a model/engine combination, we have to add in the penalties for power hungry options and extra weight items, as all these eat away at the figures. But who is doing that, when they option the panoramic sunroof, heated seats, or big rims with power sapping tyres?

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