Vehicles modified with alternative fuels

An alternative fuel system is an option sometimes considered by vehicle owners looking to manage their fuel costs or reduce their environment impact. The most common alternative fuels types currently used in vehicles are Liquefied Petroleum Gas (LPG), Liquified Natural Gas (LNG) and Compressed Natural Gas (CNG).

Liquefied Petroleum Gas (LPG) is the generic name used for mixtures of hydrocarbons, primarily propane and butane. These mixtures change from a gaseous state to a liquid when lightly compressed.

LPG is odourless, colourless and heavier than air and a chemical is added to give it a distinctive smell, so that even a very small leak can be easily detected.

Is the LPG used in a car different to that used in a BBQ?

Yes. There are two separate blends or grades of LPG and they cannot be interchanged. The LPG used for automotive use is a mixture of butane and propane while the LPG used for barbecues, camping etc is a blend of propane only.

Liquified Natural Gas (LNG) is a clear, colourless, non-toxic liquid that is produced when natural gas is cooled to -161°C at atmospheric pressure. 

By liquefying natural gas, its volume is reduced approximately 600 times. This makes it easier and cheaper to transport over long distances and to store it in large quantities. Odourant cannot be added as it interferes with the liquefaction process. As a result, all LNG vehicles where the container is mounted in the interior of the vehicle has a continuous monitoring natural gas detection system installed within the compartment.

LNG is best suited to the heavy transport sector.


Compressed Natural Gas (CNG) is a fossil fuel substitute for petrol, diesel or LPG. 

It’s the compressed form of the gas commonly used in homes throughout Australia for domestic cooking and heating appliances. It’s made by compressing natural gas to less than 1% of the volume it occupies at standard atmospheric pressure. It is stored and distributed in hard containers at a pressure of 200–248 bar (2900–3600 psi), usually in cylindrical or spherical shapes. 

CNG consists mainly of methane (80 – 95%), a colourless, odourless and tasteless gas. The distinctive smell associated with it is an additive which enables quick detection of leaking gas. 

CNG is most commonly used in traditional internal combustion engine cars that have been converted into bi-fuel vehicles (petrol/CNG).


Own a vehicle fitted with an alternative fuel system?

If you’re looking for information about managing a gas fuel system modification that you’ve made – or are planning to make – to your vehicle, visit our page about vehicles with gas fuel systems.

Looking for information about providing gas fuel systems services? 

To work in Victoria on vehicles that are fitted with gas fuel systems, you must enter into an Alternative Fuel Systems Assessment and Certification Scheme (AFSACS) Agreement with VicRoads. 

This scheme replaces the former requirement to be registered with the Automotive Alternative Fuels Registration Board, known as AAFRB (on 1 January 2020, responsibility for regulating and supporting the alternative fuels industry transferred from the AAFRB to VicRoads).

Learn more about Alternative Fuels Systems and Certification Scheme (AFSACS) Agreements.

Are you a technician?

You can only work on gas fuel systems in vehicles if you have acceptable trade and training qualifications and are an Associate Technician employed or contracted to an approved AFSACS provider. 

Learn more about becoming an AFSACS Associate Technician.

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