Elgas LPG Gas Blog

What is LPG Autogas? Gas Conversion - Auto LPG Fuel vs Petrol

The fuel type LPG used in LPG powered cars is quite often called “Autogas”

In auto LPG vs petrol cars, auto LPG offers advantages in fuel economy and maintenance costs, as well as reduced emissions.

Auto LPG Fuel: What is Autogas? What is the Difference between Autogas and LPG

Autogas is LPG for vehiclesLPG – Liquefied Petroleum Gas – is a flammable hydrocarbon gas fuel including propane, butane and mixtures of these gases also known as Autogas. There is no difference between Autogas and LPG except the possible inclusion of butane along with the propane.

Autogas, liquefied through pressurisation, is a fuel that comes from natural gas processing and oil refining and is also referred to as natural gas liquids – NGL.

The fuel type LPG (Autogas) is used as fuel for vehicles.

In different countries, what is supplied can be propane, butane or propane-butane blends.

What is an Auto LPG car or other LPG Vehicles?

Auto LPG cars run on LPG Autogas fuel, 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 auto LPG conversion systems:

1. Converter-and-mixer systems

2. Vapour phase injection (VPI)

3. Liquid phase injection (LPI)

4. Liquid phase direct injection (LPDI)

Difference Between Auto LPG and Petrol

Auto LPG is a liquefied gas whilst petrol is a liquid at normal atmospheric pressure. LPG cost less than petrol and generally has a higher octane rating, at over 100 octane. Regarding cost, the fuel type LPG is about half the price vs petrol cars but you will use about 20% more LPG that petrol. The cost saving is more pronounced if you compare against similar octane petrol.

The result is that you still save about 40% on your fuel costs especially when comparing to high octane petrol.

This savings will more than cover the cost of the LPG conversion, if you are a driver that racks up a high kilometre count.

What are the Pros and Cons of Buying an LPG Powered Car?

LPG Autogas carsPros:

• Autogas fuel cars have lower running costs.

Auto LPG may actually prolong engine life.

• Autogas fuel 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,

• Auto LPG fuel octane ratings over 100 allows for higher compression ratios, which can increase power output.


• The biggest negative is the extra cost involved in buying an LPG car or converting a car to LPG fuel.  However, the cost is typically recovered quickly through the realised savings.

• In some countries it may be a bit more difficult to find an LPG service station but, in most countries, they are becoming more numerous every year.

Types of Auto LPG Conversion Systems

How does an LPG engine work?

• Converter-and-mixer systems are the oldest style, dating back decades and still widely used.

The LPG 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 fuel instantly vaporises, cooling the combustion chamber fuel-air mixture during the compression stroke, with further performance and emission improvements. 

Types of Auto LPG Vehicles Using Autogas Fuel

Autogas LPG conversion of an SUVAutogas fuel 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.

Auto LPG Hybrid Tri-Fuel

Camry LPG hybrid conversion

Take the best automotive technology – hybrid drive – and marry it with the cleanest and most economical commercial fuel – Auto 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.

Auto LPG Fuel Octane Rating

The fuel type LPG Octane rating is over 100. This auto LPG (Liquefied Petroleum Gas) Octane rating allows for higher compression ratios, which can increase power output.

The Auto LPG octane rating exceeds all production vehicle Octane requirements, which typically peak out at an Octane rating of 98.

Environmental Benefits of Auto LPG Fuel

The creation of carbon dioxide (CO2) is appreciably less with an Auto LPG vs petrol car.

Diesel CO2 emissions are 29.2% higher than LPG fuel whilst petrol is 26.8% higher than LPG.

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.

Auto LPG vs petrol 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 LPG vs petrol and diesel cars is the near-absence of particulate matter (PM) emissions.

Popularity of Auto LPG Fuel Worldwide

After ethanol, the fuel type LPG (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 Auto LPG Fuel Incentives

Governments in many countries actively encourage the use of auto LPG fuel, 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 fuel fleet would still be on the move.

Auto LPG Fuel is Easily Available

Autogas stations are easy to find. There are over 3,000 Autogas fuel outlets in Australia. 

In fact, we have one of the most extensive autogas distribution networks in the world.

Auto LPG Fuel Cars are Safe

Autogas LPG cars are safeIn many ways, auto 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 fuel 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 fuel 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.

Auto LPG fuel 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 auto LPG 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.




View More LPG Gas Blogs

Comments, questions or feedback?

Please Email us at: This email address is being protected from spambots. You need JavaScript enabled to view it.

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.