Malaysian automaker Proton has launched a new 'ecoLogic' versions of its Gen-2 model line able to run on either petrol or liquefied petroleum gas (LPG).

Normally it costs GBP1,500-2,000 to convert a car to run on fuel costing GBP0.58 per litre vs GBP1.12 for petrol but Proton is selling the ecoLogic models at the same price as the petrol-only equivalents.

It said fuel consumption increases slightly on LPG but buyers should still save around 40% on their fuel costs based on an average annual mileage of 10,000.

The LPG cars also have a three-year/60,000 miles warranty and three years of RAC breakdown cover.

LPG is a popular conversion for large petrol SUVs here in the UK. Proton reckons there are over 140,000 vehicles running on the fuel in the UK and 11m worldwide.

Humberside Police has been running LPG-converted Proton vehicles for over 10 years and, with just over 300 on their current fleet, have saved up to GBP300,000 on fuel costs per year.

Citing Fleet News, Proton said residual values on LPG dual fuel vehicles were recently found to be up to 7.4% better than their petrol equivalents.

The automaker said there are over 1,400 refuelling sites around the UK, including motorway service stations and major supermarkets.

Proton claims the ecoLogic GEN-2 is more eco-friendly than petrol and diesel-powered cars because LPG produces less carbon monoxide, particulates and nitrous oxides than other fuel sources, and engines running on it emit 15-20% less carbon dioxide than petrol units.

The ecoLogic engine starts on petrol and switches to LPG when it's most efficient to do so, usually after about 20 seconds.

Inside, a switch on the centre console shows the fuel level and there is a second filler cap next to the petrol cap, which is matched to the colour of the car. The LPG tank is in the spare wheel well, so owners lose only a relatively small amount of boot space.

Launch models are also being offered with a 'free' leather interior, normally a GBP1,000 option.