There is increasing evidence suggesting that real-world fuel consumption and CO2 emissions improvements in the last decade have been much lower than the officially reported ones. Scientific studies show that the offset between officially reported values and real-world vehicle CO2 emissions in Europe has constantly increased over the last years.

A recent report by the European Commission's Joint Research Centre, identifyies possible ways to deal with the CO2/fuel consumption gap between officially reported and actual emissions in vehicles. In particular, it suggests the fleet-wide monitoring of real-world fuel consumption, together with model-based tools able to provide customized information to road users.

The report presents also experimental evidence on the variability of the CO2/fuel consumption of vehicles, putting into question the idea that a single central estimate of these quantities may be sufficient.