The average driver does not drive in a "controlled trial". www.honestjohn.co.uk/realmpg shows what the average of what real drivers experience in real life situations given a variety of different driving conditions and driving styles and relying on various methods of recording the mpg, either from the dash meter (always complimentary), to brim to brim, and even brim to brim with corrected odometer readings. So, being an average of an average of an average, it gives the fairest measure of what most drivers are likely to achieve. The latest Focus 1.0 EcoBoost Econetic is 99g/km CO2, so is free VED.