THE Toyota Prius may already be a petrol saver, but a team of researchers hopes to squeeze even more fuel efficiency out of the hybrid car.

GP Batteries is collaborating with the National University of Singapore (NUS) to road-test a Prius modified in Hong Kong that can be charged from an electric socket and run fully on electricity.

That would save about 3 litres of petrol a day for a typical motorist whose daily commute to and from work makes up the bulk of his travelling. The conversion cost? About $16,300.

The team's aim is to study the plug-in hybrid electric vehicle's performance in Singapore's climate and driving conditions. GP Batteries' director of special projects Wong Kin Pun explained that batteries are sensitive to temperature and Singapore's tropical climate can affect the performance of the battery, which was originally designed in the US.

City driving, with frequent starts and stops, is also vastly different from cross-country driving. There is therefore a need to collect data from the vehicle to re-calibrate the battery.

So far, the converted Prius can travel about 30km purely on electricity. It takes four to six hours to fully charge the car and juicing up the battery will add $1.20 to your utility bill. But Mr Wong said that it is still early days yet and the modification of Priuses on Singapore roads will take time.

Road test for 'electric' Prius