More than a million people have used the What Car? True MPG web tool since it was launched a year ago - and some eyes have been opened.Editor-in-chief of the UK automotive magazine, Chas Hallett, said: “We launched What Car? True MPG April 2012 as a direct answer to the countless readers who had contacted us to say how disappointed they were with their car’s fuel economy figure. "Expecting high fuel efficiency and getting the opposite can double a household’s fuel expense. What Car? True MPG is a solution to this problem – the online tool gives Britain’s car buyers the most realistic fuel efficiency information possible – and it’s free.”LESS THAN 5% CORRECTThe web tool testing programme revealed that 95.5% of cars do not match the fuel consumption figures produced in the laboratory-based British government tests. The average miles per gallon (litres/100km) shortfall across all cars tested was 17%.Surprisingly, the car segments with the largest difference between government data and real l/100km were city cars and superminis; SUV’s showed the least disparity.Hallett added: "It is vitally important for people to buy the right car for their lifestyle. For example, there is a general misconception that smaller cars automatically give better fuel economy. That’s not the case: if you use a small-engined car for long motorway runs every day, it will not be that economical. A larger-engined car would be much better suited.”The What Car? True MPG tests also revealed that a number of cars do deliver on stated fuel consumption that some models even bettered published data.Here are the cars that exceeded the official published government average consumption1 Mazda 3 2.3 MPS: +9.7%2 Nissan 370Z 3.7 V6: +6.8%3 Volvo S60 3.0 T6 AWD 304 auto: +4.6%4 Volvo XC90 2.4 D5 200 auto: +3.2%5 Ford S-Max 2.0 TDCi 163 auto: +1.5%6 Peugeot 5008 2.0 HDi 150: +0.4%7 Volkswagen California 2.0 TDI 140: 0%8 Toyota GT-86 2.0: 0%9 Subaru BRZ 2.0: 0%The web tool tests cars on real roads in the conditions that every motorist faces each day. What Car? has now tested more than 500 new cars and data from those tests is being used by the web tool to produce personalised, realistic fuel consumption data.Until now, the only information available was the automakers’ own figures which are conducted in laboratory conditions on rolling roads.