In a report produced for the Australian Automobile Association (AAA), research firm ABMARC claims that its own tests, carried out in Victoria with a sixth-generation 2010 Volkswagen Golf 103TDI diesel wagon – before and after its software update had been applied – revealed an average increase in fuel usage of 7 per cent.
"This ranged from using 2 per cent more fuel while driving in urban areas, 7 per cent more fuel on rural roads and 14 per cent while driving on highways," the AAA says in its statement announcing the result of the tests. The 70-page report can be read here. (PDF link, 5.16mb)
UPDATE, March 13: Volkswagen has responded aggressively to the AAA's report. See further down for VGA Managing Director Michael Bartsch's full statement.
The model, equipped as tested with a six-speed DSG automatic transmission, lists official NEDC-based fuel consumption figures of 5.7L/100km on the combined cycle, 4.7L/100km in highway driving ('extra urban') and 7.3L/100km in urban driving.
The report also notes a 41 per cent reduction in NOx emissions after the software update (tested on a warm start), still four times higher than accepted laboratory limits.
Among the findings of ABMARC's tests is confirmation that the software fix "has not detrimentally impacted vehicle performance."
"A slight increase in power and torque was observed post-fix. The on-road performance from standing and rolling starts was not affected," the report reads.
The AAA is aligned with the Fédération Internationale de l'Automobile (FIA), and its commissioned testing was carried out with that body's support.
In a statement issued today, Volkswagen Group Australia said it "rejects the comparison sought to be made by the AAA."
"The KBA (the German motor authority) approved Volkswagen's software update on the basis that it did not adversely affect the emissions or fuel economy of vehicles in test conditions," the company said.
"Several reputable automobile organisations in Germany, Austria and Switzerland have since tested vehicles and concluded that vehicles continue to perform as expected after the software update. These [organisations] are aligned with the AAA.
"The vehicles continue to satisfy European and Australian emissions standards following the application of the update to the engine control software. Some 42,000 Volkswagens in Australia and more than 6 million globally have had the software upgrade."
In Europe, motoring clubs ADAC, ÖAMTC and TCS (somewhat equivalent to the groups represented in Australia by the AAA) delivered a largely positive report in 2016 on their tests of Dieselgate-affected Golf and Audi models, claiming "consumption and engine performance are hardly affected" by the software fix.
Like the AAA, those organisations claim their tests were carried out with the support of the FIA.
UPDATE, March 13: In addition to the above quotes, Volkswagen Group Australia has now released a full statement, describing the AAA and ABMARC test as one based on a "flawed methodology" with "glaring inconsistencies". The full text is below.
“While the PEMS testing procedure used by the AAA may in principle be appropriate for testing emissions of nitrogen oxides, due to the high PEMS tolerances of ± 10%, it is simply not suitable for testing fuel consumption and CO2 emissions,” said VGA Managing Director Michael Bartsch.
“Furthermore, major flaws which render the tests wholly unfit for purpose included substantial variations in the test runs and atmospheric conditions both on the same vehicle and different vehicles and even the performance of different vehicles being compared.”
The AAA tested a Golf Wagon both before and after it received the voluntary software upgrade, which has been applied to more than 6 million cars globally.
“The so-called new test results are not new and were published by AAA early 2017 and sank without a trace,” Mr Bartsch said. “This is cynical opportunism based on the timing of an important trial in the Federal Court.”
“As far as VW vehicles are concerned, on-road testing by reputable motorists organisations in Germany, Switzerland and Austria show the opposite results to those arrived at by the AAA.”
“The differences between laboratory tests and on-road testing results are well known and the ACCC has worked with all automobile manufacturers on approved wording, which Volkswagen Group members use in Australia, to ensure that this is properly disclosed to consumers.”
Mr Bartsch said that Volkswagen is an enthusiastic proponent of real world testing of vehicles for NOx emissions, and supported the recent introduction of new test cycles in Europe which better reflect real world conditions.
The Dieselgate recall currently underway in Australia includes a software fix for Audi, Volkswagen and Skoda models driven by 1.6- and 2.0-litre versions of the group's EA189 diesel engines, while some have also required a minor hardware update.
Volkswagen says the fix has so far been applied to around 42,000 of nearly 100,000 vehicles recalled in Australia (among six million globally).
The issue affects around 11 million vehicles globally and has cost the Volkswagen group more than $30 billion in fines and settlements in the United States. A Volkswagen executive has also been jailed in the US.
In Australia, where emissions standards are not as strict, the consequences of Dieselgate have been limited to a software update – approved by the Department of Infrastructure and Regional Development (DIRD), the body responsible for overseeing vehicle compliance.
Australia's Federal Court is currently hearing cases brought by consumer watchdog the ACCC, along with a class action seeking compensation for owners.
In Europe, the authority to deal with the issue lies with national governments, making Dieselgate a more complex and fractured issue. In addition to this, German website The Local reports that Europe's car-making countries are reluctant to carry out any hard-hitting investigations or hand down penalties as severe as those given in the US.
And, while Volkswagen secured approval for its software update from Germany's KBA, Berlin-based Handelsblatt reports that the organisation is set to be restructured, with authority over new-vehicle checking and approval to be split across new departments.
Volkswagen is not the only company to have been caught in diesel emissions test cheating, with others also recalling and upgrading millions of vehicles in Europe. Fiat Chrysler was sued in 2017 by the United States' Environmental Protection Agency (EPA).