You are (understandably) missing the point. About 15 years ago, the EC originally legislated that the only fuel economy figures that could be mentioned by manufacturers were those from the official EC lab tests. At first, these were reasonably realistic. Then the EC started turning the screws down on CO2 emissions, which are extrapolated from the fuel economy figures. So the only way car manufacturers could achieve increasingly lower CO2 was to tune their engines very specifically for the ECDC lab tests. The result is low CO2 for taxation purposes. But completely unrealistic fuel economy figures. For real figures, go to honestjohn.co.uk/realmpg These are supplied by real drivers driving real cars in real UK road conditions. Obviously these conditions will vary, as does the means by which the drivers judge their fuel economy, which might be by dashboard indicator, by brim-to-brim calculation, or even by odometer corrected brim-to-brim calculation. But they all go into the same pot and collectively give an average of an average of an average. And this is the only figure you can take to be truly representative.