Record fuel prices have sent many Australians searching for alternative options to lower their fuel bill, such as hybrids and PHEVs.
Some have decided to skip the fuel bill altogether and make the jump to an electric vehicle.
You might've noticed many service stations still offer LPG as a fuel source alongside the normal petrol and diesel bowsers – but does the near-forgotten gas still hold up in the current times, will it cost you less, and can your car run on it?
LPG (liquefied petroleum gas), often called Autogas, is a mixture of propane and butane stored under pressure as a liquid in a tank – and is an abundant resource in Australia.
Vehicles can be converted to run on LPG, but much of the fuel's former popularity came from Australian-made cars built to run on it.
Holden, Ford, and, in the early 2000s, Mitsubishi have previously offered versions of their locally-built models which are either powered solely by LPG, as in Falcons and Magnas, or can be switched between petrol and LPG, as in Commodores.
Converted LPG vehicles are regular petrol cars that have been converted to run on LPG, which involves setting up a new fuel system with injectors, a tank and a regulator.
Usually, the original petrol system is still in place, enabling the driver to change between fuels – dubbed a dual-fuel system.
LPG costs considerably less than petrol, even when compared to 91-octane fuel at the current price, which soared easily above $2.50 a litre.
At the time of writing, the average price of LPG is $1.13/litre in Sydney, $1.05/litre in Melbourne, $1.10/litre in Brisbane and $1.41/litre in Perth, compared with $2.45/litre, $2.40/litre, $2.44/litre and $2.44/litre for 91-octane petrol, respectively.
LPG has a far lower carbon/hydrogen ratio than petrol; burning LPG produces less CO2, therefore less tailpipe emissions.
However, there is a catch – read more below.
LPG is not as energy-dense as petrol, and depending on the driving style and vehicle, LPG vehicles tend to be less fuel efficient, so the fuel is not as cost-effective as it initially seems.
LPG contains 24.4 MJ/litre of energy, while petrol has about 32 MJ/litre, meaning that 1.3 litres of LPG is needed to provide the same energy as one litre of petrol.
The vehicles that run LPG are also not as efficient. For example, a Ford Falcon XR6 powered by LPG claims fuel economy of 14.9 litres per 100 kilometres, while an equivalent petrol automatic version quotes 10.1L/100km.
Still, it would cost $16.84 to cover 100km in the Falcon on LPG at $1.13/litre, compared with $24.75 on 91-octane regular unleaded petrol at $2.45/litre.
LPG cars need their gas cylinders rested and recertified every 10 years to ensure the system can support the higher pressures that the alternative fuel requires.
There are also limited workshops that will conduct LPG conversions these days and the conversion itself is quoted to cost between $1500 to $4500, depending on the type of vehicle.
Unlike 15 years ago, when LPG was common during local manufacturing, it is now much harder to come by. Even in the major cities, some searching and travel is required to find the fuel.
Further inland, it is close to extinction and becomes harder to find. Be prepared to see it no longer offered one day, as demand dwindles.
Can I fill my car with LPG?
Unless your car was built from the factory or converted to run on LPG, you cannot.
LPG is stored as a liquid under high pressure in a specialised, heavy steel cylinder, normally fitted in or under the boot of the car. The fuel tank of a petrol car cannot hold the pressure required to store LPG as it is made of plastic or thinner steel.
Before LPG can be used in an engine, it must be converted from liquid to a vapour using a vaporiser.
Unlike petrol engines, LPG requires a special mixer or injector system to be added to the intake manifold to feed the gas into the engine.
To handle the altered air-fuel combination required for LPG, the vehicle's electronic control unit must be tuned.
Do any new cars run on LPG?
The short – and true – answer is no.
Fuel-efficient hybrids and plug-in hybrids have all but killed the fuel, particularly after the arrival of the first Camry Hybrid in 2012, with Holden ending production of LPG cars locally in 2015, and Ford following in 2016 upon shutting its factory doors.
It's been more than 10 years since factory LPG cars were sold in Australia, so these cars, even the newest examples, are now a decade old.
But a large number of LPG cars are available on the second-hand market and, in Europe, there is a market for compressed natural gas (CNG)-powered vehicles, an adjacent technology to LPG.
