Fuel-economy ratings for cars sold in Europe have long been wildly unrealistic, sometimes more than 30 percent more optimistic than real-world consumption figures.

Today, that will change.

As of September 1, two new and more stringent testing regimes are to be used for certifying new vehicles going on sale in European Union countries.

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The test cycles in use until now, known as the New European Driving Cycle or NEDC, have been widely criticized as too gentle and unrepresentative of actual usage patterns for modern vehicles.

The first new test to be performed in laboratories, known as the Worldwide harmonized Light vehicles Test Procedure, or WLTP, was designed to be far more representative of real-world driving cycles than the NEDC tests in use since 1996.

A second set of tests will actually measure the emissions from vehicles driven on real roads in a wide range of conditions, using portable emission-measuring devices.

Diesel fuel pump

Diesel fuel pump

Known as the Real Driving Emissions or RDE test, it will make Europe the sole place where vehicles must be certified using actual operating conditions rather than solely in labs.

The European auto manufacturer group known as ACEA issued a statement saying it welcomed the new tests, which apply to both gasoline and diesel vehicles as well as electrified models.

They will, it said, "provide a more accurate basis for measuring a vehicle's fuel consumption and emissions."

CHECK OUT: Used diesel demand drops in Germany over fear of software upgrades

The group stressed that the newest diesel vehicles, certified under the most recent set of the phased Euro 6 emission limits, will operate within the real-world testing cycles.

That's likely a response to the fallout from the two-year-old Volkswagen diesel emission scandal, which has hurt public confidence in diesel vehicles.

It has also resulted in buyback programs by most major automakers for the dirtiest diesels, those certified under Euro 4 or earlier before 2007.

2014 Range Rover Evoque SD4 (European diesel model), ZF Drive Day, Jul 2013

2014 Range Rover Evoque SD4 (European diesel model), ZF Drive Day, Jul 2013

German makers will also update more recent diesel vehicles with powertrain control software changes to ensure they stay within emission limits under all circumstances.

That, in turn, has caused a fall in prices for used diesel models due to worries over whether the modified used cars will remain as fuel-efficient and continue to offer the same performance as they did before updates.

The British magazine Autocar has a nice piece giving more details on the new test cycles, including the larger number and greater duration of the various test cycles used—including those for plug-in hybrid and battery-electric vehicles.

[hat tip: Miguel Angel]


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