Report: Europe’s Fuel Efficiency Ratings Off by 25%

New-car fuel economy ratings in Europe are grossly higher than consumers can expect in real-world driving conditions, according to an analysis by the International Council on Clean Transportation.

The Washington, D.C.-based group says the gap between lab ratings under the New European Driving Cycle and actual on-road results climbed from less than 10% in 2001 to about 25% by 2011. Its analysis says the gap for automatic and manual transmission vehicles is about 26% and 22%, respectively.

The ICCT worries that the increasing shortfall is making consumers skeptical about fuel economy ratings and thus less likely to invest in fuel-saving technologies.

The report blames the problem on Europe's highly reproducible, laboratory-based "type approval" certification process. The ICCT acknowledges that variations in individual driving styles make it difficult to define real-world results. But it says that problem can be overcome by aggregating on-road driving results.

The gap began to widen five years ago when several European countries switched to vehicle taxation systems based on carbon dioxide emissions. The ICT suggests carmakers have taken advantage of the test rules and allowances to improve their CO₂ results under the NEDC test.

In Germany, average lab-certified CO₂ for new cars dropped 19% from 180 g/km in 2001 to 146 g/km by 2011. But the analysis says real-world emissions declined only 7% from 193 g/km to 179 g/km over the period.

The ICCT favors a switch to the Worldwide Harmonized Light Vehicles Test Procedure being developed by the United National Economic Commission for Europe. The WLTP aims to establish a more realistic laboratory driving cycle that factors in actual resistance forces on a moving vehicle. It also seeks to limit current allowances in the NEDC that permit carmakers to improve results by temporarily boosting tire pressure, realigning the wheels and testing only vehicles with the lowest weight and fewest options.