We've all done it. Stood there tipping an endless stream of liquid money into the fuel tank of our car, thinking that there must be a leak somewhere as it couldn't need that much juice, surely? Then hopping back in and checking the trip computer only to see that we'll pretty much need to top up again before the end of the road. Our cars are quite simply not living up to their quoted fuel performance.
Thankfully though, it's not our fault; it's actually partly the car companies' fault and it's all down to the fact that they're potentially cheating on their tests. Well, cheating is perhaps too harsh a word; the problem is that, in the official government fuel consumption tests, car makers are virtually encouraged to do everything they can to make the numbers look good, even if they can never be realistically replicated in the real world.
So they strip out weight as much as possible, even down to leaving items like the spare wheel behind. Some use good old gaffer tape to cover up the gaps between the car's panels to make it more aerodynamically slippery. They make sure the oil and transmission fluids are as new and as perfectly lubricating as possible. They disconnect the alternator so that it's not a drain on the engine's performance (it's only a short test so no one will notice the battery's not charging). And finally, they pump up the tyres near to bursting to reduce their rolling resistance. All cheats, but all fine, dandy and legal under the current EU and UN fuel testing systems.
"The reason motorists don't see fuel economy claims translate into reality is that car makers are gaming the vehicle testing system" said James Nix, of An Taisce - the National Trust for Ireland, adding that "it's an easy system to manipulate because manufacturers do things during the fuel cycle test that drivers would never do. They aren't breaking any rules here; the loopholes loom so large that car manufacturers can massage fuel economy results without being in formal breach of EU rules."
The gap between the test and reality is no small matter, not something that can be brushed away with claims of 'natural variability' or some such dismissal. In fact, according to UK environmental pressure group Transport & Environment, the real world fuel consumption can be worse than the official test by a margin of as much as 20% or even 50%.
"The gap between official driving tests and real world driving is growing" said a reports commissioned by Transport & Environment. "In Germany that gap has increased from 7% on average in 2001 to 23% in 2011 and consequently only half the anticipated improvement in fuel economy (of 1.0l/100km) has been achieved on the road. For drivers, this is adding around €2,000 to the fuel costs of the vehicle over its lifetime. Data from Germany is supported by other studies from The Netherlands and Switzerland. The growing gap is leading drivers to become increasingly distrustful of official data on fuel economy, making them less likely to consider buying a more fuel efficient vehicle."
Now, that closing statement is pretty sweeping and ignores the fact that, across Europe and the world, buyers are flocking to buy vehicles that are vastly more efficient than their predecessors. It's also worth noting that while it's very true that many, if not all, cars will fail to reach their quoted consumption in everyday driving, on-the-road experience has lately shown us that many new models can easily break the 50mpg barrier, even the 60mpg one - quite an advance on a decade ago.
Nonetheless, if the claims about car makers regularly prepping their cars in this manner for fuel tests are accurate, then we are being defrauded at some level. That was borne out last year in the US when both Hyundai and Kia were ruled to have over-estimated the fuel economy of several key models. Following several lawsuits and hearings, the US authorities ordered Hyundai and Kia to cough up cold hard cash to compensate buyers who weren't getting their claimed gas mileage. Could the same happen here? Easily...
In the UK, What Car? magazine conducted a series of tests of some of the most common, and supposedly economical, cars on the market and they all missed their quoted fuel marks. Not by a small amount, but by as much as 25mpg in some cases. Chas Hallett, What Car? editor-in-chief, said "with rising fuel prices, the miles per gallon issue is high on every motorist's agenda. Countless car buyers are frustrated that they don't match the official government fuel figures.
"Some eco cars are very good around town and in an urban environment. But the minute you drive them on a motorway then they don't do so well. Against this background, buying a Toyota Prius may be a perfect choice for some people who drive around town a lot, but not for others who may spend a lot of time on motorways."
Car makers will of course say that they are simply putting their best feet forward and getting the best possible out of the car allowed by the test and that, really, is fair comment. It's the holes in the testing schedule that are to blame, and you can hardly castigate car makers for exploiting every tool in their armoury, at a time when CO2 emissions and fuel consumption have become as much unique selling points as they are technical data. But it leaves consumers, and their wallets, out in the cold.
The proposed New European Driving Cycle (NEDC) test should eliminate many, if not all of these loopholes, as well as providing a more realistic, real-world estimation of fuel consumption. But, its implementation is being resisted because it will drive up CO2 emissions figures and that is a financial no-no for the car makers. Which puts us back, at the pumps, where we started.