If a car can run 3,000km on a litre of petrol, how much is needed in the tank to drive from Singapore to Kuala Lumpur?

About a third of a can of Coke, or just over 100ml, to cover the 360km trip.

Rising to this challenge - taking green to the extreme - are students from the National University of Singapore (NUS), who have built the university's first eco-car. Their vehicle will compete against European designs in next week's Shell Eco-marathon, a race to crown not the fastest, but the most fuel-efficient car on the track.

Held in Nogaro, France, the race will see some 256 student teams, mainly from across Europe, competing for the top prize of 1,500 euros (S$3,100). The heart of the NUS' 3m-long Hope07 vehicle is a 34cc petrol engine modified from a lawn mower.

It took five third-year mechanical engineering students three months to build the car, with help from NUS alumni at local engineering consultancy Hope Technik and the DSO National Laboratories.

The single-seat car travels at a top speed of 75kmh and is about 10 times more fuel-efficient than normal cars.

But do not expect to see this engine on the roads any time soon.

Aside from being 'hot and stuffy', the vehicle is an exercise in research rather than commercialisation, said Hope Technik engineer Peter Ho.

The project is a stepping stone to gain further insight into engine design and understanding how modifications to engine parts can help improve fuel efficiency, explained Professor Lim Seh Chun, head of NUS' department of mechanical engineering.

The team is realistic and does not expect to win the race.

"We just want to go there and learn from other teams," said student driver Yeo Yicong, 24. "Hopefully we'll build a better car next year."