Most manufacturers have a ‘green’ range of extra-economical vehicles these days – usually with some sort of ‘eco’ prefix…

Often these cars differ from standard vehicles in relatively minor ways – there will be a small styling tweak to improve aerodynamics here or a lengthening in the gear ratios there.

Even changing the tyre type can make a significant difference to fuel consumption.

Now Malaysian firm Proton has entered the ‘green’ fray with ecoLogic versions of its Gen-2 model.

These cars do not have particularly low emissions; nor is their fuel consumption among the best in class.

But the ace up the ecoLogic GEN-2′s sleeve is that it is able to run on liquefied petroleum gas (LPG) as well as petrol. Which means you’ll be paying around 50p a litre for your fuel instead of up to 90p for a gallon of unleaded.

This translates into savings of up to £500 annually, depending on your mileage. Nor do you have to pay for the conversion job – the cars come pre-converted and can run either on LPG or unleaded.

You’ll need to keep some petrol in the tank to get the car started and serve as a back-up. Other than that you can start to enjoy filling your tank for around £20 instead of £40.

Once the engine has fired up on petrol, it switches automatically to LPG after around 20 seconds. The gauge for this fuel is located by the handbrake, so don’t be taken in by the fact that the fuel gauge on the dash barely moves. If you run out of LPG it will start dropping soon enough.

The Proton has two filler caps – one for petrol and the other for LPG. It’s a straight forward matter to refuel – you need to make sure the fuel nozzle is locked on to the correct filler cap. The LPG tank is located in the spare wheel well, so you do not lose too much boot space.

If you can’t find an LPG outlet you just use petrol instead.

I tried a saloon version of the car which costs £10,795 to put on the road. A hatchback is available for another £200.

The car came with a sporty-looking rear spoiler and a smart paint job but some of the panel gaps were wider than is generally the case these days.

Specification is high, however, with standard features including parking sensors, air conditioning with pollen filter, electric front and rear windows, automatic central locking and alloy wheels. Leather seats are a £1,000 option.

The test car had a smart interior finished in black and red. It came with a properly integrated stereo system -Ênot always the case with cars from the Far East.

Performance is reasonable and the steering was sharper than I had been expecting. Cars running on LPG do not run quite as efficiently as on petrol. There is a marginal effect on performance but it’s barely noticeable.

While the car is reasonably refined it does suffer from wind noise, particularly from the spoiler, at motorway speeds.

Protons generally do not have class-leading residual values but I would expect this to be more sought after because of its lower running costs.

LPG is perhaps not quite as attractive now that fuel prices have come down from the stratospheric levels of mid-2008.

But it is not unreasonable to expect some volatility and in these recessionary times all opportunities to save on running costs are to be welcomed.

By Peter Carroll