Test shows worse MPG after Volkswagen emissions fix

The fix Volkswagen is applying to diesel cars that were fitted with emissions-cheating software can have an adverse effect on fuel economy, a new test suggests.

More than 1.2 million cars sold in the UK had the software. But while Volkswagen accepted that a technical fix was necessary, and has since applied it to more than 600,000 cars, company bosses have said that no compensation will be offered, specifically because the fix doesn’t affect economy.

That claim is based on the results of back-to-back tests under the conditions used to determine official economy figures, and was verified by Germany’s motor vehicle regulatory body, the KBA.

However, Autocar magazine has now put one of the affected models through What Car?’s True MPG real-world economy test both before and after the fix, and saw a 6.1% drop in average economy: from 50.72mpg to 47.61mpg. At the same time, CO2 emissions rose from 147.3g/km to 156.9g/km.

The car tested was a 2003 Touran MPV with Volkswagen’s EA189 2.0-litre diesel engine – one of three engines sold in the UK that was fitted with the software.

True MPG tests are conducted in a laboratory to ensure repeatability within 1%, but based on a real-world route that takes in town, rural and motorway driving.

Volkswagen points to a 20-point checklist of variables that need to be taken into consideration before the company will recognise a test as valid, but Autocar was not granted access to this criteria, despite requesting it.

The True MPG test results come in the wake of a report by the Volkswagen Diesel Customer Forum (VDCF) last month that said owners of post-fix VWs with the 2.0-litre diesel engine had experienced a range of problems, including breakdowns, increased fuel consumption, reduced performance, and diesel particulate filter (DPF) failures.

Exhaust gas regeneration valves are also said to have failed, as have turbochargers and fuel injectors, while other owners report their cars having entered limp home mode or got noisier.

Volkswagen claims that many of these faults could simply be down to poor maintenance, and that some of the cars were even missing their DPFs.

In a statement it said: “Far fewer than 1% of UK customers who own Volkswagen Group vehicles that have received the technical measures have reported issues. That means that more than 99% of customers are satisfied with the application of technical measures, which of course are carried out free of charge.

"As you would expect," it continued, "we make it a priority to look at the vehicles of the very small proportion of customers who report issues.”

Read more in the latest issue of Autocar, which is on sale now

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