I've been on the radio affirming this. When the compulsory ECDC tests were first introduced they gave a reasonable expectation, and the EC decreed that the lab test figures were the only figures that manufacturers could use in any form of publicity. Since then, the screw has been turned on CO2 emissions, both in terms of VED tax, BIK tax and company car tax relief; and in terms of fines on manufacturers whose corporate CO2 output exceeds an average 130g/km in 2013. So it's hardly surprising that cars have been optimised for the EC tests and because these test figures are the only figures that manufacturers are allowed to publicise, that is what you read. These are not 'claims'. They are ECDC test results as decreed by the EC and the only figures the manufacturers are legally allowed to give you.

The tests are so far from reality that the 'cold start' urban tests are conducted in ambient temperatures of between 20C and 30C. So naturally manufacturers heat soak the cars at 30C before they conduct the tests to minimise the cold start overfuelling. The tests do not account for diesel fuel used to regenerate diesel particulate filters to meet another EC requirement. So in answer to your question, a car will only ever get close to the EC lab test figures when driven in identical conditions to the lab tests with anything that does not have to be switched on, switched off. This is not a criticism of the ECDC cycle. Merely an explanation. I would not want the ECDC tests to become more realistic because that would lead to an increase in taxation. If you want realistic figures based on what the average driver is really getting, see honestjohn.co.uk/realmpg