His car’s official fuel economy of about 33 miles a gallon “can only be achieved on expressways,” not in Shanghai’s stop-and-go traffic, said Mr. Lu, a finance manager for a U.S. bank.
“Fuel-economy figures aren’t reliable at all in China,” he said.
The reason, say analysts and environmentalists: The testing method employed in the world’s biggest auto market falls short.
World-wide, auto testing has become a source of scandal. Just in the past year Volkswagen AG VLKAY 0.16 % has admitted to years of cheating on emissions tests, and Mitsubishi Motors MMTOY 0.00 % to decades of falsifying mileage data in Japan. In 2014, South Korean auto makers Hyundai Motor Co. HYMLY 0.00 % and Kia Motors Corp. 000270 1.32 % agreed to pay a combined penalty of $ 300 million to the U.S. for overstating fuel-economy claims.
All this is putting policy makers under pressure to roll out tougher standards.
In China the testing is carried out by the car makers themselves, and representatives of BMW, General Motors Co. GM 0.41 % , Ford Motor Co. F -0.57 % , Volkswagen, Toyota Motor Corp. TM 0.75 % , Honda Motor Co. HMC -0.33 % and Daimler AG DDAIY 0.02 % told The Wall Street Journal that their companies comply with Chinese regulations.
The problem, said Wu Zhixin, deputy director of China Automotive Technology & Research Center, a government agency that helps draft regulations, is that the current tests are outdated. “We aim to make future test cycles much closer to the real-world road conditions,” he said.
“China’s fuel-economy tests ignore some important real-world driving conditions, such as traffic congestion, air-conditioning use and bad weather,” said Kang Liping, a project manager for the Innovation Center for Energy and Transportation, a clean-transportation think tank backed by U.S. funds.
China’s roads grow ever more crowded—at the end of last year there were four times as many cars as a decade before, and only 35% more road. The official test simulates city driving in stop-and-go traffic by running the cars at between 20 and 50 kilometers an hour—a range set in 2004, when fuel-economy standards were introduced for some passenger vehicles. In real life, car speeds in the country’s 45 major cities last year averaged 29.6 kilometers an hour, according to Chinese online map purveyor AutoNavi Software Co., slowing to 26 kilometers an hour during rush hour.
As for the air conditioner, it can increase fuel consumption by up to a third, according to the Innovation Center, which says cars in China consume about 30% more gasoline than advertised. By contrast, U.S. drivers report mileage 12% better than official estimates, according to a study by AAA, a U.S. motorists organization.
The fuel-economy tests are conducted in labs on roller test benches. Car makers report the data to the government, and it is verified by third-party laboratories certified by the Ministry of Industry and Information Technology. The ministry didn’t respond to a request for comment.
“It’s hard to accuse manufacturers of manipulating fuel economy, because of loopholes in Chinese tests,” said Ma Yong, deputy secretary-general at the nonprofit China Biodiversity Conservation and Green Development Foundation, which is collecting information about fuel-economy discrepancies. Faced with a discrepancy between the lab results and what an actual driver gets, a car maker can cite factors like “aggressive driving habits and road congestion,” he said.
Said a BMW AG spokesman in China, “real-world fuel consumption may differ from official fuel consumption.” One sign of a discrepancy: Car makers’ own data shows many models with higher fuel-economy ratings in China than in the U.S.
Stricter test standards will be submitted to the government by the end of next year, said Mr. Wu. It’s unclear when China will adopt them. “Even if the government approves, car makers will be given a couple of years of reprieve,” he said.
For now, some Chinese drivers are taking matters into their own hands. Zhang Xiong says his Xiaoxiongyouhao app, used to track fuel consumption, has been downloaded 2.5 million times and has on average 300,000 active users every month. He created it in 2009, he said, after finding that his Chinese FAW Besturn’s fuel consumption was running around 25% higher than claimed.
“I wanted to know how to save fuel,” Mr. Zhang said. The app has recorded more than 10 million pieces of fuel-consumption data covering more than 80 brands in China.
Auto makers’ fuel-economy challenge is about to become tougher. To ease pollution and reduce fuel imports, China has ordered an increase in average fleet fuel efficiency by 2020 to 5 liters per 100 kilometers, or about 47 miles a gallon—a 27% reduction in fuel consumption from last year’s level. Manufacturers that fail will face financial penalties and restrictions on expansion and new-car launches.