The European Commission on Wednesday said EU-based carmakers are artificially inflating carbon dioxide emissions data under a new testing regime to distort future greenhouse gas targets, but manufacturers denied any trickery.
Authorities are currently switching over from an older emissions testing procedure known as NEDC to a new, globally-agreed one called WLTP.
During the changeover, "manufacturers may use the transition... to inflate their WLTP emission levels in 2020," Commission spokesman Christian Wigand said in Brussels.
Higher emissions levels in 2020 would in turn mean less ambitious targets to reduce CO2 output by 2025 and 2030, the dates by which the EU hopes to slash vehicles' production of the gas by first 15 and then 30 percent.
"Study from the Joint Research Centre (the Commission's scientific research arm) actually finds that there have been differences in declared and actual values" of CO2 emissions from manufacturers, Wigand said.
The new allegations differ in important details from the "dieselgate" scandal that has rocked the car industry since 2015.
In that case, Volkswagen admitted to manipulating millions of cars to appear to emit less harmful nitrogen oxides (NOx) in lab tests than they in fact did in real on-road driving.
Other manufacturers like Mercedes-Benz parent Daimler have since fallen under suspicion.
Without naming any individual companies, the Commission now alleges manufacturers are cheating in two ways to undermine its CO2 output targets—decided last September in the wake of the dieselgate scandal.
First, they are declaring emissions of CO2 on average 4.5 percent higher than actually measured values, with reporting for some models as much as 13 percent higher than measurements.
Secondly, officials saw "some evidence" manufacturers are configuring vehicles differently for the WLTP and NEDC tests, aiming to maximise emissions on the new tests—thus softening their future targets—while minimising them on the older regime.
"The correct implementation of this WLTP testing is of course of utmost importance" for limiting CO2 emissions, Wigand said.
"We are now following this up to make sure that no misuse can happen."
Contacted by AFP, German high-end carmaker BMW pointed to a statement from the country's Association of the Automotive Industry (VDA), which said that "German carmakers are doing everything they can" to reduce emissions to 95 grammes of CO2 per kilometre by 2021.
"Reporting higher emissions would be counterproductive," the association claimed.
A spokeswoman for car giant Volkswagen said that "testing procedures are carried out by independent institutions under neutral supervision".
"It can be ruled out that the newly measured CO2 levels under WLTP have been artificially increased for Volkswagen group's brands" which range from high-end Audi and Porsche to mass-market Skoda, she added.
Meanwhile a spokesman for France's Citroen and Peugeot manufacturer PSA said there was "no cheating" at the group, adding that it publishes all its emissions data online.
Commission officials suggest revising EU regulations to make sure measured, rather than reported, CO2 emissions under WLTP are used to define future targets.
The EU's executive body also wants to overhaul legislation on emissions targets, adding amendments including one to make sure carmakers use vehicles configured the same way for both the old NEDC and new WLTP tests.
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