LPG has been widely used in Australia as a petrol substitute.

It’s use as a motor fuel is well understood and is backed by many years of local experience. But it isn’t necessarily appropriate for every motorist, or every car.

Some LPG facts

  • Automotive LPG is a hydrocarbon fuel comprising a mix of mostly propane and butane. 
  • It isn’t the same as the LPG used in domestic applications such as BBQs. 
  • Its quality is tightly controlled to ensure consistent vehicle performance.
  • It is produced from crude oil or is stripped from Natural Gas. 
  • Australia has substantial reserves of gas and LPG should be readily available into the future.
  • It is stored as a liquid in pressurised cylinders but reverts to a gas when the pressure is released. 
  • When allowed to revert to gas it expands 270 times its liquid volume. 
  • It’s widely available in the more populated areas but you may need to plan your refuelling stops in advance when travelling in country areas.

Advantages 

  • For vehicles that travel long distances or use large amounts of fuel there are potential cost savings. 
  • Litre for litre LPG is commonly around 50 percent cheaper than petrol. 
  • Exhaust emissions are lower and engines potentially last longer.

Disadvantages 

  • The up-front cost of conversion is high. Depending on the application, conversions typically cost between about $3,000 and $4,500.
  • LPG consumption is higher than petrol. 
  • In some cases, the installation of the gas tank in the car’s boot will take up considerable space.  
  • In 4WD vehicles, where the tank is fitted under the floor, there may be some loss of ground clearance.  
  • LPG is not as widely available as petrol.

Is LPG right for me?

As much as we’d like to be able to answer this question, the reality is it depends on your individual circumstances, so only you can answer it.  
  • The economic viability of conversion will be dependent on your vehicle's fuel consumption, the number of kilometres travelled each year, the actual difference in price between LPG and petrol (you’ll need to know the average gas and petrol prices for your area), the cost of the conversion and how long you plan to keep the vehicle.
  • You must also decide what an acceptable payback period is i.e. how long it will be before the fuel savings equal the cost of the conversion. It’s only then that you’ll start saving money.
  • The calculation table below will help you determine how much converting to gas will save you and how long it will take to repay the cost of conversion.
The figures shown in the table below are provided as an example only. You will need to substitute your own figures into the right-hand column, and do the simple step-by step calculations. 

lpg costs calculation table

* Based on a theoretical 30 percent increase in fuel consumption when operating on LPG

LPG fuelled used cars. Another option

LPG fuelled vehicles can be found on the used car market.  

  • These may offer a cheaper alternative to having your existing vehicle converted.   
  • The value proposition and pay-back period for an existing LPG fuelled car would be significantly more attractive than for a new conversion due to the lower capital cost. 
  • If you are considering the purchase of a used LPG fuelled vehicle, the usual advice applies – have it inspected prior to purchase by someone who knows what they’re looking at.

Other considerations 

  • Not all vehicles can be easily converted to run on LPG. 
  • Conversion kits are usually only developed for relatively common vehicles to spread the costs. 
  • The energy content of LPG is lower than petrol so fuel consumption and power will suffer. 
  • Depending of the vehicle and type of system fitted, fuel consumption could increase by as much as 30 percent.
  • While fuel cost savings can be achieved, real savings are only realised once the conversion cost has been recouped.  This may take a considerable period. 
  • Some engines can have durability issues and may need other modifications or require additional servicing.

Types of conversions

Dual-fuel 
Dual-fuel means a vehicle that has two complete fuel systems and can operate on either of the fuels, usually petrol or LPG. 

Dedicated gas 
A dedicated gas vehicle will have no petrol fuel system so it can only operate on LPG. The advantage is they can be optimised for use with LPG, which offsets the power loss and fuel consumption increases usually associated with dual fuelled engines.  The disadvantage is that you will need to ensure that LPG is available in your area.

LPG and diesel engines 
Diesel engines generally cannot be converted to operate on LPG. However, there are systems that will allow a diesel engine to operate on a mixture of diesel and LPG to increase power and reduce fuel costs. Guidance should be sought from the vehicle’s manufacturer before committing to such a system.

Warranty cover

Factory fitted or factory approved systems will usually be covered by the vehicle’s warranty. However, any problems related to non-factory approved equipment will not be covered by the vehicle’s warranty.  Gas systems will generally come with a warranty that should cover its fitment, the equipment, and any related problems.  Not all engines are suitable for gas conversion, so we recommend checking suitability with the vehicle’s manufacturer prior to conversion.

The final word

Do your research:

  • There can be technical factors that will influence the vehicle’s suitability for conversion and you should discuss this with the vehicle’s manufacturer and gas system installers.
  • Talk to owners of similar vehicles to get some real-life feedback about the conversion.
  • Discuss the proposed conversion with several installers if possible. Ask how many of your type of vehicle they’ve converted and what, if any, problems they’ve encountered.
  • Ask if any additional servicing or maintenance over and above the vehicle manufacturer’s requirements is needed, as this could increase operating costs and will need to be factored into your payback period calculations. 
  • Be cautious of requirements for additional tappet adjustments as this could indicate an underlying durability or ongoing service issue.

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