Car users will finally have officially-verified figures on the mileage of all cars sold.

The Society of Indian Automobile Manufacturers had, in a move backed by the government, asked its members to make available their mileage data for verification by the Automobile Research Association of India.

The ARAI is a government agency under the ministry of heavy industry. The verification is after test-drives of each model at the ARAI's facility at Pune.

The data has been released. Expectedly, Tata's Nano is the most fuel-efficient, giving 23.6 km to a litre of petrol.

Next comes Fiat 500, which runs on diesel; it gives 22 km for each litre.

Next to Nano in petrol efficiency is Maruti Suzuki's A-Star. It runs 19.6 km on a litre.

The listing is for car makers who are members of Siam and excludes Audi, Volvo and Volkswagen.

The move is part of an effort by both manufacturers and the government to provide customers a reliable guide instead of independent claims by each company. It is also part of a broader auto fuel policy formulated by Siam, the Bureau of Energy Efficiency and the Petroleum Conservation and Research Association to promote fuel-efficient vehicles.

Industry analysts say the display of mileage data will help buyers take informed decisions.

"Studies conducted by us reveal this fact. Customers who were over-promised on mileage developed dissatisfaction that was four times higher than customers who were promised the actual mileage. So, the resultant transparency actually boosts the brand image of the car manufacturer," said Mohit Arora, senior director of Singapore-based JD Power and Associates.

Arora adds the current method of mileage declaration leaves much to be desired. "In the US, it is mandatory that each car for sale sport a mileage sticker on its windshield so that the customer cannot miss it."

Maruti Suzuki was the first company to display ARAI-certified mileage figures for its models, from January 1.

"The move has strengthened the confidence customers place in our brands. After all, the figures we quote are not supplied by us but by a third party, the ARAI," said Mayank Pareek, executive officer (marketing & sales), Maruti Suzuki.

At the entry-level segment, the Nano tops the list. Its closest rival is the Maruti 800, with 16.1 km/litre.

Then there is the A2 compact segment. Here, as mentioned earlier, the A-Star, launched last year, wins the trophy. Its 19.6 km a litre is better than the Alto's 18.1 km. Among the diesel variants in the segment, the Fiat 500 runs 22 km on a litre.

In the mid-size segment, Honda City and Hyundai Accent are winners in the petrol category. Both deliver 16.1-16.5 km on a litre of petrol.

Maruti Swift Dzire is the next in the petrol category, with 15.9 km/litre. Among diesel variants, Hyundai Verna, with 21.9 km per litre, is the winner.

In the executive car segment, Honda Civic is the first, with 15.5 km/litre, while Skoda Octavia delivers 21.39 km/litre of diesel. The Mercedes C-class diesel C220 CDI gives 13.9, while the BMW 3 series (diesel) gives 15.9 km/litre.

In the premium segment are Hyundai Sonata, Skoda Superb and Toyota Camry, all around 13.54 km/litre. The top diesel models in this segment are Skoda Superb and BMW 520 D (15.7 km/litre).

The luxury category has Mercedes Benz as the winner in both petrol and diesel categories. The Mercedes S350 L travels 9.9 km/litre of petrol, while its diesel counterpart, the Mercedes ECDi, logs 11 km/litre.

In the utility segment, in the category up to 3.5 tonnes, the Honda CRV wins in petrol, logging 13.2 km/litre, while both Hyundai Tucson and BMW X3 travel more than 14 km on a litre of diesel.

In the five-plus-tonne category, GM's Chevrolet Tavera tops with 13.6 km/litre of petrol, while Mahindra Maxx HT wins in diesel, notching 14.4 km/litre.

In the multi-purpose vehicle segment, Maruti Omni is the winner, with 16.9 km/litre, while Tata Motors [Get Quote] Ace Magic is the little champ, travelling 21.5 km on a litre of diesel.