Two of Australia's most popular mid-sized luxury SUVs, both engineered in Germany, have been found to have fuel consumption as much as 20 per cent higher than that claimed by the manufacturer.
The latest round of Federal government-sponsored "real world" fuel consumption and emissions tests have found that the BMW X3 exceeded the laboratory fuel test outcome by 20 per cent while the Audi Q5 was 17 per cent higher.
Both the German SUVs also emitted more CO2 than they recorded in the laboratory. The 2.0-litre turbo-diesel Audi emitted 17.5 per cent more CO2 while the 2.0-litre turbo petrol BMW produced 23 per cent more.
And one of the most affordable new small cars sold in Australia, the $19,990 Chinese-built MG3 hatchback, was another dismal performer under the testing procedure.
Out in the real world it used 19 per cent more fuel than the car maker's laboratory test and produced 13 per cent more CO2.
Conversely, the darling of Australia's rental and fleet buyers, the 2.0-litre automatic Hyundai i30 passenger car - which for Australia has a much bigger engine that as sold in Europe - had a consumption only 1 per cent higher than the "rolling road" laboratory test and its CO2 outcome exactly matched that of the lab test.
The latest tranche of results from the Australian Automobile Association's real world testing program add further impetus to the Federal government's plan to roll out a tough new national fuel efficiency standard, where fines and penalties will be applied to companies which don't achieve pre-determined targets on fleet averaged emissions.
The Federal government and climate groups have long maintained that Australian motorists are paying much more in fuel costs per year than in Europe and the US, where automotive emissions and efficiency standards apply, and that Australia was becoming a "dumping ground" for high-emitting vehicles because it didn't set a standard.
But that will change from January next year when the new laws come into effect.
The final phase of the consultations finishes on March 4.
The AAA's public program, which uses a scientific test rig set up on the cars as they are all driven on the same test route, has badly exposed how lab tests are not a proper guide for consumers.
And the longer the "real world" testing program continues to expose these glaring anomalies, the more that trust in what data vehicle manufacturers claim is eroded.
This erosion of trust arrives at a bad time for many car importers, which for decades have been represented by the richly funded Canberra lobby group Federal Chamber of Automotive Industries, as they are scramble to work out how to reshape their future product line-up beyond next year so as not to incur any financial penalties.
The AAA, Australia's peak motoring consumer body, supports the rollout of an efficiency standard but for "fairness" and "transparency" wants the Federal government to release the full economic modelling, produced by consultancy ACIL Allen which underpins it. The government has so far steadfastly refused to release this modelling.