HOLDEN has partially resolved one of the main hurdles to buying an LPG-powered Commodore: boot space.

Its new dedicated gas Commodore has its fuel tank under the floor of the boot, instead of between the rear wheel arches. This allows full use of the boot space and gives access to the ski port in the otherwise fixed rear seat.

At least that's the case if you are happy with a tyre inflation kit. If you want the optional space-saver spare wheel or the full-sized spare then they sit on top of the boot floor and pinch load space.

Holden says the gas-only engine is more powerful, uses less fuel than the previous dual-fuel system and, with a larger 84-litre tank, has a longer range.

The 3.6-litre V6 engine produces 180kW, or about 12kW more than the previous dual-fuel version but 20kW less than the petrol-only engine.

Fuel use drops to a combined best of 11.8 litres per 100km, down from 13.4l/100km when running on LPG in the dual-fuel engine.

The engine also has low exhaust emissions of 189 grams of CO2 a kilometre, easily passing the latest standards and scoring 4.5 out five in the Green Vehicle Guide.

With the price of LPG less than half that of unleaded petrol, the lower running costs of LPG are well established. This has to be offset against the additional cost of the LPG option - $2500, less the $2000 Government rebate for private buyers, or $500.

Holden has expanded the LPG option to include sedan, wagon, ute and long-wheelbase models.

The LPG engine still uses a sequential vapour port injection system in which the liquid LPG is vapourised before entering the engine, unlike Ford's liquid injection system which sprays liquid into the engine.