What is LPG Autogas?
Gas Conversion – LPG vs Petrol

The LPG fuel used in LPG powered cars is quite often called “Autogas”.
Autogas offers advantages in fuel economy and maintenance costs, as well as reduced emissions.

What is Autogas?

Autogas is LPG – Liquefied Petroleum Gas – a flammable hydrocarbon gas including propane, butane and mixtures of these gases.
Autogas, liquefied through pressurisation, comes from natural gas processing and oil refining.
Autogas is used as fuel for vehicles.
In different countries, what is supplied can be propane, butane or propane-butane blends.

What is an LPG car?

LPG cars run on LPG Autogas, with 25 million worldwide.
LPG cars can be OEM single fuel models or dual fuel LPG conversions that run on either LPG or petrol.

There are four types of LPG conversion systems:

  1. Converter-and-mixer systems
  2. Vapour phase injection (VPI)
  3. Liquid phase injection (LPI)
  4. Liquid phase direct injection (LPDI)

What are the Benefits of Autogas?

Autogas cars have lower running costs.
Autogas is less expensive than petrol or diesel.
Engine oil and spark plugs need changing less often with LPG, so service costs are reduced.
Environmental benefits include reduced particulate, CO2 and NOx emissions.
Octane ratings over 100 allows for higher compression ratios, which can increase power output.

Types of LPG Conversion Systems

  • Converter-and-mixer systems are the oldest style, dating back decades and still widely used.
  • The liquid fuel is converted into vapour and then mixed with air before going into the intake manifold.
  • Vapour phase injection (VPI) systems use a converter-and-mixer system, but the gas exits the converter under pressure and is injected into the intake manifold.
  • Electrically controlled injectors improve the metering of fuel to the engine, fuel economy and power, as well as reducing emissions.
  • This has been the most popular type system in recent years.
  • Liquid phase injection (LPI) systems inject liquid directly into the intake manifold, where it vaporises, not using a converter.
  • The fuel vaporising in the intake manifold cools and increases the density of the intake air, substantially increases power output, improves fuel economy and has lower emission, when compared to VPI systems.
  • Liquid phase direct injection (LPDI) are the most advanced systems, injecting liquid LPG directly into the combustion chamber.
  • The LPG instantly vaporises, cooling the combustion chamber fuel-air mixture during the compression stroke, with further performance and emission improvements.

Types of Vehicles Using Autogas

Autogas is primarily use in cars and light commercial vehicles.
Autogas has been very popular with SUV and utility vehicles owners.
Fleets, and taxis in particular, were early adopters and big users.
Generally, there are less in the way of heavy duty vehicles converted but there has been significant use of Autogas in the US school bus sector.
Most Autogas vehicles are after-market conversions, usually converted shortly after the original vehicle purchase.
Some OEM vehicle manufacturers are now producing and marketing dedicated Autogas vehicles with conventionally placed fuel tanks.

LPG Hybrid Tri-Fuel

Take the best automotive technology – hybrid drive – and marry it with the cleanest and most economical commercial fuel – LPG – and the result is nothing short of amazing.
The Toyota Camry Hybrid, with its petrol-electric hybrid drive, is already one of the most economical cars on the market.
Add a state-of-the-art LPG liquid injection system to the Camry Hybrid and you have an ultra-efficient tri-fuel vehicle that is truly revolutionary.
Hybrid LPG is the new benchmark in fuel economy and hybrid LPG conversions are available now.

Environmental Benefits of Autogas

Using Autogas creates appreciably less carbon dioxide (CO2) than unleaded petrol.
CO2 is the primary greenhouse gas causing long term climate change.
When examined from a “Well to Wheel” perspective, the CO2 benefit is even greater.
This includes emissions associated with the processing and transportation, as well as use.
Diesel CO2 emissions are 29.2% higher than LPG whilst petrol is 26.8% higher than LPG.
LPG cars also produce 95% less ozone and smog causing NOx than diesel engines.
The dirty black smoke that we see coming from diesel vehicles is fine particulate matter.
These fine particles may be deeply inhaled into the lung and carry with them a collection of attached hazardous compounds.
Experts at the World Health Organisation (WHO) say diesel engine exhaust fumes are carcinogenic.
One of the key environmental advantages of Autogas over diesel, as well as petrol, is the near-absence of particulate matter (PM) emissions.

Popularity of Autogas Worldwide

After ethanol, Autogas is now the highest volume alternative automotive fuel in use worldwide.
Global Autogas consumption rose 24% between 2009 and 2014, reaching over 26 million tonnes.
There are now more than 25 million Autogas vehicles in use globally and almost 73,000 refuelling stations.

Government Autogas Incentives

Governments in many countries actively encourage the use of Autogas, for environmental reasons.
Government financial incentives, aimed at subsidising the conversion cost of the vehicle, are very effective in promoting Autogas use.
Autogas surpasses gasoline and diesel in the majority of studies, conducted around the world, comparing environmental performance.
Autogas emissions are especially low with respect to noxious pollutants.
This has become critically important in places like London and South East Asia.
For example, government environmental restrictions on the use of diesel vehicles have helped drive the success of Autogas in Korea and Japan.

Security of Supply

If all oil and refinery imports were stopped, for reasons of war, natural disaster or other unforeseen circumstances, Australia would grind to halt within a matter of weeks.
Unlike petrol and diesel, for which we are reliant on these imports, Australia is self-sufficient in and a net exporter of LPG.
So, while other vehicles would become unusable if imports were cut off, Australia’s LPG fleet would still be on the move.

Autogas is Easily Available

Autogas stations are easy to find.
There are over 3,000 Autogas outlets in Australia.
In fact, we have one of the most extensive autogas distribution networks in the world.

LPG Autogas Cars are Safe

In many ways, LPG fuelled cars are safer than their petrol counterparts.
LPG fuel tanks are typically made from welded heavy gauge steel, in contrast to modern petrol tanks that are plastic.
They are much more puncture resistant and will survive much greater impacts than a typical petrol or diesel tank.
Autogas tanks are designed with an Automatic Fill Limiter (AFL) to prevent overfilling so the release of excess fuel during the refuelling process is virtually eliminated.
On the other hand, most of us have experienced petrol spills, which will puddle under your car, whilst any fugitive LPG just dissipates into the air.
Sealed passenger compartment ensure that no LPG enters the passenger compartment of the vehicle.
Autogas tanks are designed to withstand even the most extreme conditions, with 20% unused volume to allow for any expansion of the LPG in hot conditions.
There are electronically controlled shut-off valves which stops the flow of gas to the engine if the engine stops for any reason or in the event of an emergency.
LPG is also less likely to catch fire than petrol as petrol (gasoline) ignites at temperatures as low as 246°C while LPG (propane) ignites at 470°C.

Strict Standards

Australian LPG Autogas safety standards have been refined over many years.
LPG fuel systems for vehicle engines are covered under Australian Standard AS1425.
The Standard specifies the requirements for the design and construction of component parts and for their installation in vehicles, as well as for tests, commissioning, and periodic inspection.
This Standard defines the minimum requirements of acceptability.
The specifications and requirements of AS1425 are some of the most stringent in the world.

Trained & Authorised Technicians and Certification

The mechanics that work on LPG vehicles are required to have more training than an ordinary car mechanic.
Specific schooling and knowledge, relating to Autogas systems, is a requirement.
All conversions also require certification.
On completion of an aftermarket installation, the installer will supply a certificate of compliance with AS1425.


Comments, questions or feedback? Please Email us at: blog@elgas.com.au

The information in this article is derived from various sources and is believed to be correct at the time of publication. However, the information may not be error free and may not be applicable in all circumstances.