Fuel consumption figures quoted by the government are often both inaccurate and unreliable, says the car review website dogandlemon.com. Editor Clive Matthew-Wilson says:

“Our actual road tests show that it’s rare to find a vehicle where the claimed fuel consumption figures match reality.”

“It’s important to realise that the fuel consumption figures quoted by the government aren’t based on actual driving by actual people – they’re conducted in a laboratory by the car companies themselves. These figures are then passed on to the public as if they were gospel.”

Matthew-Wilson is particularly concerned about the habit of quoting so-called ‘average’ mileages. These figures are obtained by combining estimated figures for fuel consumption on the open road with estimates for round-town motoring. This so-called average may be wildly inaccurate, he says.

“For example, according to the official government figures, a Toyota FJ Cruiser uses an average of 11.4 litres of petrol per 100 kilometres. However, in the real world, this vehicle averages nearly 14 litres per 100 kilometres. Around town – which is where most of these vehicles will spend their days – the fuel consumption will be over 18 litres per 100 kilometres. That’s nearly 60% higher than the so-called average figure quoted by the government.”

Matthew-Wilson said manufacturers’ fuel consumption figures for smaller cars tended to be more accurate than their figures for larger cars.

“Any modern vehicle will give reasonable fuel economy on long straight roads; it’s the round-town economy that matters. A two-tonne four-wheel drive is going to use a lot of fuel simply moving away from traffic lights. By comparison, a one-tonne car is going to require far less fuel to get it moving.”

However, says Matthew-Wilson, hybrid cars are often nowhere near as economical as they are claimed to be.

“According to the BBC, government fuel consumption figures for hybrids are often out by around 30%, and our own tests confirm that.”

“The government website says that the Prius uses an average of 3.9 litres per 100 kilometres. In the real world, independent tests have shown the Prius uses an average of 5.3 litres per 100 kilometres. Around town, the Prius’s fuel consumption can easily rise to about 7.4 litres per 100 kilometres. That’s nearly twice the average figure that the government and Toyota are quoting.”

Recent road tests by the independent British consumer watchdog Which? showed that the Prius gives worse fuel economy than a sporty BMW 3-Series diesel. Matthew-Wilson adds:

“It’s easy to come up with impressive fuel economy figures if you drive slowly down long, clear roads or on a factory test track. It’s also easy to come up with impressive fuel economy figures in a laboratory. However, the only fuel economy figures that really matter are the ones achieved by ordinary motorists on a daily basis.”