Originally Posted by philtrick123
This debate makes me wonder what the true MPG is going to be for the 18d that's recently launched.
The drive in the UK seems to be to lower CO2 for tax purposes. But the lower CO2 doesn't translate to real world lower MPG.
Hardly any cars will give anything like the official figures, unless driven very lightly in light driving condtitions.
1-series doesn't do well as it is a blunt, stubby body form, so driven at speed will start drinking fuel more so than the average saloon/sedan, from my experience.
The whole testing system needs revision, but no system will be perfect, as once we move the goalposts the manufacturers obviously design to achieve the next set of tests. Happened before, when we used to have the 56 & 75mph constant speed driving in the older test regime. Some cars were so badly geared to achieve the best 56mph figure, they were so inflexible in real world driving, it was common to use more fuel in the economy model, that the more sportier cars in the range.
Honest John's site gives a reasonable feel for what models and engines give best figures, and which have the greatest mpg shortfall.
In my 5-series, the 535i touring is rated far closer to official figures at 91% of official figures, (my driving reflects that is pretty accurate for the average) whereas the 535d is 74% of the official figure. That closes the real world gap average to less than 3mpg, so very different to the over 10mpg difference in the official figures. The tests favour the diesel, so petrol engines look far worse on paper.
But that is typical of reality, when we crunch the numbers.