EU scientists find VW car more polluting after Dieselgate 'fix'

According to the source, who is close to the JRC, researchers found that emissions were higher than before Volkswagen “fixed” the car, which is an SUV model.

A second source confirmed that the JRC had planned to test the Volkswagen Tiguan, but could not confirm the results.

Another EU source said the information could not be confirmed "at this stage".

The source added that "the commission is not running market surveillance tests" but "is closely following VW's own commitments to bring the engines affected by manipulations to full conformity with the applicable type-approval rules."

After Volkswagen's emissions fraud was detected in the US in September 2015, the company promised to remove the emissions cheating part of the software from its 8.5 million diesel cars driving around in Europe.

Volkswagen promised the software update would be carried out by the autumn of 2017, and that it would not negatively affect the car's emissions.

The JRC, the European Commission's in-house science body, has one of Europe's most advanced emissions testing laboratories, and regularly tests cars on the road.

It has always baffled politicians how VW would be able to remove the cheating software without worsening the car's emissions performance – after all, why would the cheating software have been necessary in the first place if the fix were so simple?

The promise that Volkswagen could remove the illegal cheating software without negatively impacting emissions was viewed with scepticism already in a hearing in the UK's House of Commons, some months after the scandal broke.

“It just does not seem to make sense,” said MP Will Quince in a January 2016 hearing in the House of Commons with Volkswagen engineer Oliver Schmidt and managing director of Volkswagen UK, Paul Willis.

“There is a relatively easy fix, which Mr Schmidt tells us you have done via a software upgrade,” added Quince.

According to the Volkswagen witnesses, that was possible because technology has advanced in the past ten years. But that still left the question as to why the emissions software had not been updated before.

“If that is the case, and it has been there for 10 years, why did you need to put in the defeat device in the first place?,” said MP Huw Merriman.

Schmidt and Willis did not have an answer. Schmidt is now in custody in the United States.

The report on higher emissions followed numerous reports from Volkswagen owners that their cars' fuel efficiency had worsened after being treated post-Dieselgate.