TESTS have revealed the fix being applied to cheating Volkswagen diesels could be causing fuel economy figures to drop.
An independent investigation on a 2003 VW Touran – fitted with the 1.6-litre diesel – found discrepancies between figures before and after the software update was completed by VW.
Economy fell from 50.72mpg to 47.61mpg, while CO2 emissions were up from 147.3g/km to 156.9g/km.
However, dangerous NOx emissions which were the target of the cheating scandal were halved after the fix was applied from 0.639g/km to 0.351g/km.
The tests were conducted by Autocar at Millbrook Proving Ground to a repeatable real-world test cycle using the latest international industry-standard equipment for testing vehicles.
However, VW disputed the findings and said there were more than 20 variables that can impact economy tests.
And it insisted its technical fix has no impact on a car’s performance or economy.
A VW spokesman said: “It should also be noted that the relevant approval authorities have approved the technical measures and that during the development of the technical measures, “Volkswagen worked with care to ensure that fuel consumption figures in the homologation cycle and on the road remain the same when compared with the previous software.
“If increases in fuel consumption were detected during the development phase, the software was revised and retested.”
So far, more than 600,000 of 1.2million VW models fitted with the affected EA189 model have had the recall completed.
And this latest question mark over the fix only adds to growing concern among owners.
The Sun Online’s exclusive investigation revealed a number of owners did not feel safe driving their cars anymore after they lost power on the motorway.
And the Volkswagen Diesel Customer Forum claims hundreds of its members have reported engine breakdowns, DPF failures and drops in fuel economy since having the recall done.
A poll of more than 500 owners revealed 87 per cent had experienced mechanical problems post-fix and some even claimed they’d been told by franchised dealers NOT to have the fix carried out.