New Delhi, June 3: This is a question you’d surely ask yourself while buying a car: how much petrol does it guzzle compared with other models?

Such fuel-efficiency data exist — they are collected regularly during government-mandated tests on cars sold in India. But a shroud of secrecy cloaks the results, with neither the testing agency nor the manufacturers willing to make them public.

Indian buyers are thus forced to rely only on word of mouth, automobile trade journals and the carmakers’ sales pitches to assess mileage (kilometre per litre) and choose a model.

Five years ago, the government had adopted a policy that suggested carmakers be forced to declare fuel economy in km/litre, or km/kg for every model. But the proposal was never enforced, government sources said.

“So, consumers in India are denied crucial fuel-consumption data that could have helped them make informed choices,” a senior government official said.

Yet, the fuel-consumption figures for car models sold in India are available in foreign countries where governments have made the disclosure of fuel economy mandatory.

An Australian government website, for instance, lists the fuel economy readings for several car models that are sold in India, including some models from an Indian manufacturer.

A mandatory driving-cycle fuel-consumption test on each car model to be sold in India, conducted by the Pune-based Automotive Research Association of India (ARAI), does yield values for km/litre.

“The fuel-consumption data from the ARAI test is held as a trade secret,” said Anumita Roychowdhury, a researcher with the New Delhi-based NGO, Centre for Science and Environment.

The spokesperson for the Society of Indian Automobile Manufacturers (Siam) said India does not require manufacturers to conduct fuel-consumption tests.

“The driving-cycle test (at the ARAI) is not done specifically to evaluate fuel consumption,” the spokesperson said. “The test does give us a value, but it might not be the best a vehicle can deliver.”

A fuel-consumption test has to be ideally done at sea level when a vehicle is moving in fifth gear at 50km/hour, in no-wind conditions and with all the windows rolled up, the spokesperson said. “Such a test is not mandatory in India.”

But experts argue that even the figure obtained during the ARAI test would help consumers compare cars — since all models will undergo a standard test.

“Obviously, several factors can influence fuel consumption, but the results of a uniform test applied to all models could help consumers compare apples with apples,” a government official said.

“It’s time the government enforced fuel-consumption standards,” CSE’s Roychowdhury said.

The CSE had yesterday cited ARAI test results on carbon dioxide emissions to claim that the fuel economy of petrol and diesel cars sold in India after 2005 is on an average lower than the fuel economy of those sold between 1996 and 2005.

The automobile industry and a senior ARAI official today said such a comparison would be improper because the variety of cars in India had ballooned in recent years. Cars are also heavier today.

“There’s a lot more emphasis on safety now than before. A collapsible steering wheel alone adds about 4-5kg weight to a car... and when such additional weights are added up, it affects the fuel economy,” the Siam spokesperson said.