What Are the Three Types of Fuel?

If you've ever stood at a servo staring at five different bowsers wondering which one is for what, you're not alone. The range of options at a modern petrol station has grown well beyond the simple petrol vs diesel choice most Australians grew up with. And with EVs, hybrids, and alternative propulsion entering the mainstream, the question of what type of energy source your vehicle needs is becoming more relevant than ever.

But before we get into the full picture, it's worth starting with the classic three types that have powered Australian roads for decades , petrol, diesel, and LPG. These remain the dominant options at the vast majority of servos across the country, and understanding the difference between them is the foundation of making smart choices about how you power your vehicle.

This guide covers all three core types in detail, then looks at where things are heading , ethanol blends, hydrogen, and electric , so you have the complete picture of the energy landscape Australian drivers are navigating right now.

Type 1: Petrol (Unleaded Petrol)

Petrol , also called gasoline in North America and other parts of the world , is the most widely used vehicle fuel in Australia. It powers the majority of passenger cars, most SUVs, and a large portion of light commercial vehicles on Australian roads.

Petrol is a refined petroleum product derived from crude oil. Through the refining process, crude oil is separated into fractions based on their boiling points. Petrol sits in the lighter fraction , it evaporates easily, mixes with air readily, and ignites cleanly under a spark from the spark plug.

How Petrol Engines Work

Petrol engines use a spark-ignition system. A precisely metered amount of petrol is mixed with air, compressed in the cylinder, then ignited by a spark plug. The rapid combustion of the air-fuel mixture drives the piston down, turning the crankshaft and producing mechanical power. This cycle repeats hundreds of times per minute across all cylinders simultaneously.

Petrol Grades Available in Australia

Australian petrol stations sell petrol across three main octane grades:

•       91 RON (regular unleaded/ULP) , the standard base grade; ethanol-free; suitable for most naturally aspirated passenger vehicles

•       E10 (91 RON with up to 10% ethanol) , same octane rating as regular 91 but contains renewable ethanol; slightly lower energy per litre; compatible with most post-2005 vehicles

•       95 RON (premium unleaded/PULP) , higher octane; no ethanol; required by many turbocharged and high-compression engines

•       98 RON (premium plus) , highest widely available octane grade; specified or preferred by high-performance engines and many European vehicles

Which Vehicles Use Petrol

Petrol is the default choice for:

•       Most passenger cars, hatchbacks, sedans, and wagons

•       Many SUVs and crossovers , particularly smaller and medium-sized models

•       Performance and sports cars

•       Many motorcycles and scooters

•       Small engines , lawnmowers, generators, chainsaws (non-diesel variants)

Petrol: Pros and Cons

Advantages	Disadvantages
Widely available across all of Australia	Higher CO2 emissions than diesel per unit of energy
Suitable for a huge range of vehicles	Lower energy density than diesel , uses more per km
Engines generally cheaper to manufacture and service	Petrol degrades faster in storage than diesel
Smooth, quiet operation	Not suitable for heavy towing or hauling applications
Multiple octane grades for different engine requirements	Price volatility affects weekly running costs

Type 2: Diesel

Diesel is the second major fuel type and has been a cornerstone of Australian transport infrastructure for decades. It powers most heavy-duty vehicles , trucks, buses, trains, and agricultural equipment , and has become increasingly popular in passenger vehicles, particularly SUVs, utes, and family wagons, since the late 1990s.

Like petrol, diesel is refined from crude oil, but it sits in a heavier fraction of the refinery process. It doesn't evaporate as readily as petrol, has higher energy density, and ignites through compression rather than a spark.

How Diesel Engines Work

Diesel engines use compression ignition , there's no spark plug. Instead, air is compressed to a much higher ratio than in a petrol engine , sometimes 16:1 or higher compared to around 10:1 for petrol. This extreme compression heats the air to a very high temperature, and when diesel is injected into that hot compressed air, it ignites spontaneously.

This compression ignition process is what gives diesel engines their characteristic torque characteristics , the high compression ratio and injection timing deliver strong pulling power at low engine speeds, making diesel the natural choice for vehicles that need to haul heavy loads.

Diesel Grades in Australia

Australian diesel is available in several grades:

•       Standard diesel (regular diesel) , the baseline grade available at all servos; meets Australian fuel quality standards; suitable for all diesel passenger and commercial vehicles

•       Premium diesel , available from major brands including Shell V-Power Nitro+ Diesel, BP Ultimate Diesel, and Caltex Techron Diesel; includes enhanced additive packages for injector cleaning and improved performance; recommended for modern diesel engines with common rail injection systems

•       B5 and B20 biodiesel blends , diesel containing 5% or 20% biodiesel derived from plant or waste oils; available at some independent and specialist outlets; requires confirmation of vehicle compatibility before use

Which Vehicles Use Diesel

•       Heavy commercial vehicles , semi-trailers, buses, coaches

•       Dual-cab utes , HiLux, Ranger, BT-50, Colorado, Triton, D-Max, and similar

•       Large SUVs and family wagons , LandCruiser, Prado, Fortuner, Everest, Pajero

•       European passenger cars , many BMW, Mercedes, Volkswagen, and Peugeot models

•       Agricultural and construction equipment , tractors, excavators, harvesters

•       Marine engines , many commercial and recreational vessels

•       Trains and large industrial equipment

Diesel: Pros and Cons

Advantages	Disadvantages
Higher energy density , more km per litre than petrol	More expensive per litre than petrol at the bowser
Excellent low-speed torque for towing and hauling	Diesel engines typically cost more to purchase and service
Lower CO2 emissions per km than equivalent petrol	Produce higher particulate and NOx emissions if not maintained
Longer engine life in many commercial applications	DPF (diesel particulate filter) can be problematic for short-trip driving
More stable in storage than petrol	Not suitable for small engines , lawnmowers, chainsaws etc.
Better suited to sustained highway load	Higher purchase price for diesel vehicles in most segments

Type 3: LPG (Liquefied Petroleum Gas)

LPG , Liquefied Petroleum Gas , was once an extremely common alternative fuel in Australia, particularly through the 1990s and 2000s when government subsidies and significantly lower pump prices made it economically attractive for high-mileage drivers. At its peak, Australia had one of the highest rates of LPG vehicle use in the world.

LPG is a byproduct of natural gas processing and oil refining, primarily composed of propane and butane. It's stored under moderate pressure as a liquid but converts to gas when it enters the engine's fuel system. In automotive use, it's typically referred to as Autogas.

How LPG Engines Work

Most LPG vehicles in Australia are converted petrol vehicles , they run a dual-fuel system where the engine can switch between petrol (usually for cold starts) and LPG (for normal operation). Pure-LPG factory vehicles also exist but are far less common. The LPG vapour is mixed with air and ignited by the spark plug in the same basic process as petrol.

The Decline of LPG in Australia

LPG use has declined dramatically over the past decade. Several factors contributed:

•       Government LPG conversion subsidies ended , the major financial incentive for converting to LPG was removed

•       Factory LPG vehicles were phased out , Ford Falcon LPG and Holden Commodore LPG, the most popular factory-LPG options, ceased production when those models ended

•       LPG infrastructure has contracted , many bowsers that once sold Autogas have been converted to other uses, making LPG less convenient to find

•       The price advantage narrowed , as petrol prices fluctuated, the cost-per-km advantage of LPG became less compelling

LPG still has a presence in fleet operations, taxis, and some commercial vehicles, but for most private passenger vehicle owners, it's no longer a practical mainstream option.

LPG: Pros and Cons

Advantages	Disadvantages
Lower price per litre than petrol	Declining availability , fewer Autogas bowsers nationally
Lower CO2 emissions than petrol	Significant cost of conversion for existing vehicles
Suitable for high-mileage fleet operations	Reduced boot/cargo space for the LPG tank
Cleaner combustion , less engine carbon buildup	Factory LPG vehicles no longer manufactured in Australia
Still economical for heavy fleet use	Less practical for most private owners today

Petrol, Diesel, and LPG: Side by Side

Factor	Petrol	Diesel	LPG
Energy density (MJ/L)	~32–34	~38–40 (higher)	~26 (lower)
Typical pump price (AUD/L)	$1.80–$2.10	$1.90–$2.20	$0.80–$1.00
CO2 emissions per km	Moderate	Lower per km (higher per L)	Lower than petrol
Engine type	Spark ignition	Compression ignition	Spark ignition
Towing suitability	Moderate	Excellent	Moderate
Availability in Australia	Universal	Universal	Limited and declining
Best for	Passenger cars, SUVs, performance	Heavy loads, long distance, commercial	High-mileage fleet (legacy)

Beyond the Classic Three: Other Fuel Types in Australia

The three-type framework is a useful starting point, but the picture of how Australians power their vehicles is evolving quickly. Here are the other energy sources that are increasingly relevant:

E10 and Ethanol Blends

E10 contains up to 10% ethanol blended with standard unleaded petrol. Ethanol is derived from plant material , primarily sugar cane and grain crops in Australia , making it a partly renewable alternative to pure petroleum-derived petrol. It carries the same 91 RON octane rating as standard unleaded but has slightly lower energy content per litre, meaning marginally more consumption for equivalent distance.

E85 (85% ethanol, 15% petrol) is used in flex-fuel performance vehicles in Australia and is available at a small number of specialist outlets. It requires vehicles specifically designed or modified to use high-ethanol blends.

Electricity (EVs)

Electric vehicles use electrical energy stored in a battery pack to power an electric motor. There's no combustion, no exhaust emissions, and no traditional fuel tank. EVs are charged from the grid , at home overnight, at public charging stations, or at fast-charging hubs that are rapidly being deployed across Australia.

The EV market in Australia has grown significantly from 2022 onwards, with models from Tesla, BYD, Hyundai, Kia, MG, Polestar, Volvo, and others making up a rapidly increasing share of new vehicle sales. The federal government's New Vehicle Efficiency Standard and state-based EV incentives have accelerated uptake.

Electricity as a vehicle energy source has effectively created a fourth mainstream category alongside petrol, diesel, and LPG , and for metropolitan drivers with home charging capability, the running cost per kilometre is significantly lower than any liquid fuel.

Hybrid: Petrol Plus Electric

Hybrid vehicles combine a petrol engine with an electric motor and battery. They don't plug in for charging (in standard hybrid) , the battery is charged through regenerative braking and the petrol engine. The electric motor assists at low speeds and during acceleration, reducing petrol consumption significantly.

Plug-in hybrids (PHEVs) add a larger battery that can be charged from the grid, allowing short trips to be completed on electricity alone and longer trips to fall back on petrol. PHEVs effectively bridge the gap between pure-petrol and full-electric operation.

Hydrogen

Hydrogen fuel cell vehicles (FCEVs) use hydrogen gas to generate electricity via a fuel cell, which then powers an electric motor. The only emission from the exhaust is water vapour. Toyota has been a major proponent of hydrogen technology globally.

In Australia, hydrogen vehicles remain extremely limited , the fuelling infrastructure is essentially non-existent outside a small number of trials and demonstration projects. It's a technology to watch, but not yet a practical option for mainstream Aussie drivers.

CNG (Compressed Natural Gas)

CNG is used in some commercial fleet vehicles in Australia , particularly buses and trucks in major cities. It's a lower-emission alternative to diesel for heavy transport applications. CNG passenger vehicles are uncommon in Australia but more prevalent in some other markets.

How to Know Which Type Your Vehicle Uses

This sounds obvious, but it's worth being explicit , the consequences of putting the wrong fuel type in a vehicle are serious. Diesel in a petrol engine, or petrol in a diesel engine, can cause significant damage.

•       Check the fuel filler cap , most modern vehicles have a label inside the fuel flap stating the required fuel type and octane grade

•       Check the owner's manual , the fuel specification section will clearly state whether the vehicle requires petrol or diesel, and which octane grade

•       Look at the size of the filler nozzle , diesel nozzles at Australian servos are physically larger than petrol nozzles. It's technically possible to put a diesel nozzle into a petrol filler but not the reverse , this is a design feature to help prevent misfuelling

•       Check the badging , most diesel vehicles have a 'TDI', 'CDI', 'D', 'dCi', 'HDi', 'DTR', or similar badge indicating diesel. Petrol variants are typically badged with engine size alone or 'GDI', 'MPI', 'VVT', etc.

•       When in genuine doubt , ask a service station attendant or call your mechanic before filling up

What Happens if You Put the Wrong Fuel In

Misfuelling , putting petrol in a diesel or diesel in a petrol , is more common than most people think, particularly when driving an unfamiliar vehicle or after someone else has borrowed the car.

Petrol in a Diesel Engine

This is the more serious scenario. Diesel acts as a lubricant for the fuel pump and injectors in a diesel system. Petrol has no lubricating properties , when petrol circulates through a diesel fuel system, it strips lubrication from the fuel pump and high-pressure injectors, causing rapid wear and damage. If you realise before starting the engine, the tank can be drained and flushed. If the engine has been started and run, the damage can be extensive and expensive , injector and pump replacement is often required.

Diesel in a Petrol Engine

Diesel in a petrol engine is less immediately catastrophic but still a problem. Diesel won't ignite cleanly in a spark-ignition engine , the engine will typically run rough, produce black smoke, and stall. If you've added a small amount of diesel to a nearly full petrol tank, topping up with petrol to dilute it may resolve the issue. A larger amount requires draining the tank. Damage is generally less severe than petrol in diesel.

Choosing the Right Fuel Type for Your Lifestyle

If you're buying a new vehicle and the choice between petrol and diesel is part of the decision, here's a practical framework:

Choose Petrol If...

•       You drive primarily in the city with short to medium trips

•       You rarely tow or carry heavy loads

•       You prefer a lower purchase price and simpler servicing

•       You cover under 15,000–20,000 km per year

•       You want the widest possible choice of small and medium vehicles

Choose Diesel If...

•       You regularly tow a caravan, boat, horse float, or heavy trailer

•       You drive long distances on highways , diesel's higher energy density pays off over hundreds of kilometres

•       You need maximum load-carrying capacity , dual-cab utes, large SUVs

•       You cover 20,000+ km per year where the fuel economy advantage makes the higher purchase price worthwhile

•       You drive in outback or rural Australia where diesel is reliably available even when higher-grade petrol may not be

Consider an EV or Hybrid If...

•       You have home charging capability and a predictable daily driving range

•       You cover regular short-to-medium distances and want significantly lower running costs

•       You live in a metro area with good public charging infrastructure

•       You want to reduce your vehicle's environmental footprint

•       You can manage range limitations for longer trips with charging planning

The Bottom Line

The classic three vehicle fuel types , petrol, diesel, and LPG , have shaped Australian road transport for decades. Petrol remains the most widely used for passenger vehicles, diesel dominates heavy transport and high-mileage applications, and LPG has retreated from mainstream use to a niche fleet role.

But the picture is changing. Electricity is now a legitimate fourth mainstream option for Australian drivers, and ethanol blends have been part of the petrol landscape for years. Hydrogen is waiting in the wings, and hybrid technology is bridging the gap between combustion and electric.

For most Australian drivers right now, the practical choice is still between petrol and diesel , with the growing option of electric for those in metro areas with charging access. Understanding what each type does, how it's used, and which vehicles need it puts you in a much better position to make smart decisions, both at the bowser and when choosing your next vehicle.

Frequently Asked Questions

Can I use petrol and diesel interchangeably in my vehicle?

No , petrol and diesel engines are fundamentally different and cannot use each other's fuel. Petrol engines use a spark-ignition system calibrated for petrol's combustion properties; diesel engines use compression ignition calibrated for diesel's properties. Using petrol in a diesel engine strips lubrication from the fuel system and causes rapid pump and injector damage. Using diesel in a petrol engine causes rough running, excessive smoke, and fouled components. If you accidentally put the wrong fuel in, don't start the engine , call for roadside assistance and have the tank professionally drained before running the vehicle. The damage from starting an engine on the wrong fuel type is significantly more expensive than the cost of a tank drain.

Is diesel better than petrol for everyday Australian driving?

It depends entirely on how you drive and how far you travel. Diesel has higher energy content per litre, so it delivers better fuel economy on long highway runs and is significantly better for towing heavy loads. It's the right choice for utes, large SUVs, and any vehicle regularly used for commercial or heavy-duty purposes. For city and suburban driving , short trips, frequent stops, moderate distances , petrol is usually a better match. Diesel engines and vehicles carry a higher purchase and servicing premium, and the fuel economy advantage only pays back over high annual distances. As a rough guide: if you cover more than 20,000 km per year with regular towing or load carrying, diesel is likely the better value proposition. For lower mileage, lighter-duty use, petrol generally wins on overall cost of ownership.

Is LPG still worth considering for an Australian vehicle?

For most private passenger vehicle owners today, LPG is no longer a practical mainstream choice. The bowser availability has contracted significantly , finding Autogas outside major metropolitan areas or specific fleet service locations is increasingly difficult, and the inconvenience of limited refuelling options outweighs the price advantage for most drivers. The factory LPG vehicle options that once made the choice straightforward , Ford Falcon LPG, Holden Commodore LPG , no longer exist. LPG conversion of existing vehicles is still possible and is sometimes done for high-mileage fleet vehicles where the economics still stack up. For the typical Aussie private driver, the better alternative-to-petrol options today are hybrid and electric rather than LPG.