The Australian Automobile Association announced the results on Thursday, revealing 70 per cent of the vehicles tested in its latest round exceeded their lab results.
The testing also revealed another potentially alarming trend as several new and updated models promised better fuel consumption but delivered worse results.
The announcement comes five months after the federal government began enforcing its New Vehicle Efficiency Standard, and after sales figures showed hybrid and plug-in hybrid vehicles had continued to grow in popularity.
The association analysed the fuel consumption of 17 vehicles in its latest tests, examining a mix of small, medium and large SUVs, two hybrid cars, one ute, and two diesel vehicles on a 93km circuit in Geelong, Victoria.
Twelve of the 17 vehicles tested consumed more fuel than their lab tests indicated, and six exceeded the results by 10 per cent or more.
The Chery Tiggo 4 Pro recorded the worst result, surpassing its lab results by 21 per cent, followed by Toyota's Camry Hybrid at 20 per cent, and the Lexus UX SUV at 16 per cent.
The Nissan Qashqai, Subaru Crosstrek Hybrid, and Chery Tiggo 7 Pro also consumed 10 per cent or more fuel than advertised.
The motoring organisation has now tested 131 petrol, diesel and hybrid vehicles as part of its $14 million program with 76 per cent falling short of lab test results.
Only one vehicle matched its lab results in the latest round, the Mercedes-Benz GLA, although three vehicles consumed less than advertised: the BMW X5 that used 15 per cent less diesel, the Mazda CX-80 (five per cent) and the BMW X3 (three per cent).
The AAA also analysed fuel consumption from six new and updated models of vehicles tested earlier and found four recorded a larger discrepancy between lab results and real-world use.
Toyota's 2023 Camry hybrid used eight per cent more fuel than advertised, for example, while its 2025 model used 20 per cent more fuel.
New versions of the MG HS, Kia Sports and Hyundai Tucson also recorded larger gaps than before, AAA managing director Michael Bradley said, in what could prove to be a wake-up call for authorities setting emission standards.
"Real-world testing was conceived to determine whether consumers could rely upon fuel consumption figures provided by car makers at the point of sale," he said.
"But as the program has matured, it is now providing data that can help regulators track the gains made in laboratory testing for compliance and whether those gains are delivering savings for consumers."
