What is Fuel? Definition, Types of Fuels – Petrol, Diesel, CNG, LPG, Ethanol for Cars

What is fuel, along with fuel definition, types of fuels are described along with advantages, disadvantages, impacts on the environments.

Let’s explore types of fuels!

What is fuel – Definition & Types of Fuel?

When we drive a car, what is the primary thing we do? We go to petrol pump and fill the oil tank of the car and drive. Now, how the car gets the energy from the oil that it can move?

It is because of the energy stored in the oil. This oil means the fuel.

  • Chemical energy stored in the fuel & converted the chemical energy into mechanical energy.
  • The mechanical energy helps to move the car.
  • It is not only the petrol or liquid; it may be solids or gasses as well.
what is fuel definition types of fuels cars
What is fuel definition types of fuels cars

Fuel Definition

Fuel can be defined as the solids or liquids or gasses materials which produces heat energy if it burnt.

For example,

  • coal is a solid material; it produces heat energy if coal is burnt.
  • Diesel is a liquid fuel; it produces heat energy if it is burnt.

Properties of Fuels

There are few basic characteristics of an ideal fuels,

  • Ideal fuel can be easily burnt in the air.
  • Lowest impact on the environment.
  • Lowest pollution.
  • It should be cheap
  • It should release high energy.
  • Availability of the market.
  • It should not be toxic or should not contain harmful components.

Types of Fuels

Fuels are normally classified into few categories,

  1. Based on the state of fuels
    • Solid Fuels
    • Liquid Fuels
    • Gaseous Fuels
  2. Based on the occurrence
    • Natural Fuels
    • Artificial Fuels

Now, let’s see the fuel types based on state,

Solid Fuels

Solid fuels mean, as the name suggests, the fuels which are existed in solid state at normal pressure and temperature.

types of fuels solid
Types of fuels solid


  • Coal
  • Wood
  • Straw
  • Charcoal
  • Biomass
  • Peat etc.


  • Solid fuels are very easy to store.
  • Moderate ignition temperature.
  • These are cheap comparative to liquid or gaseous fuels comparatively.
  • Easy to transport.
  • Clinker is formed during burning.


  • It forms ash which is a wastage.
  • Ash handling is a separate subject which needs to be taken care.

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Liquid Fuel

Liquid fuels mean, as the name suggests, the fuels which are existed in liquid state at normal pressure and temperature.

  • These are created from dead plants or animals in the earth’s crust many thousands years ago.
  • These are flammable.
fuel types liquid petrol station
Fuel types liquid petrol station


  • Petrol
  • Diesel
  • Liquid Hydrogen
  • Biodiesel
  • Kerosene etc.


  • Easy transportation as its liquid. It is easily transported through pipes.
  • Calorific value of liquid fuels is high comparative to solid fuels.
  • No ash formation.
  • No clinker formation.
  • No dust formation.
  • Energy loss is less.
  • Less space is required comparative to the solid fuels.


  • Proper precaution is mandatory for transport.
  • Separate system needs to be taken care for transport, so it is costly.
  • Fire hazards.
  • Proper fire control plan is required.
  • Safety related problem.
  • Odour is bad.

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Gaseous Fuel

Gaseous fuels mean, as the name suggests, the fuels which are existed in the gaseous state at normal pressure and temperature.

fuel types gas station
Fuel types gas station


  • Hydrogen
  • Hydrocarbons
  • Biogas
  • Hydrogen
  • Coal gas etc.


  • Easy transportation, it can be easily transported through pipes.
  • High heat contentOpens in a new tab..
  • Storage is easy.
  • No ash formation.
  • Gaseous fuel gives very high temperature.
  • They are clean.
  • No impurities like solids.


  • Fire hazards
  • High flammability.
  • The requirements of storage tank are large.

Let’s see the types of fuels based on formations,

Natural Fuels

The fuel which is formed by natural means is known as natural fuels.

Examples of Fuels:

  • Wood
  • Coal
  • Natural gas
  • Petroleum etc.

Artificial Fuels

The fuel which is created by human beings is known as artificial fuels.

Examples of Fuels:

  • Charcoal
  • Straw
  • Producer gas
  • Hydrogen etc.

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Descriptions of 5 Fuel Types for Cars

Let’s try to understand the basics of the type of fuel, basics, examples.

Fuel Types Car Basics

Types of fuels are a big chapter. The fuel for vehicles is like blood for humans. The fuels drive the vehicle, or you can say propel the vehicle using its combustion properties.

The vehicles were released decades ago the fuel used for vehicles kept improving with the addition of additives. Alternative fuels were encouraged more in recent decades.

The depleting resources of fossil fuels lead to promoting alternative fuels like,

  • compressed natural gas,
  • liquified petroleum gas,
  • solar vehicle,
  • electric vehicle,
  • biofuels, etc.
types of fuels for cars automobiles
Types of fuels for cars automobiles

At this time there are lots of fuels used in automobiles. Most popular and known are gasoline (petrol) fuel and diesel.

  • Petrol is used for almost all the two-wheelers and commercial cars.
  • Diesel is used for heavy trucks, tractors, etc.
  • Except for these two popular fuels, there are some fuels like compressed natural gas (CNG) and liquified petroleum gas (LPG) that are getting popular among the limited number of vehicles.

Alternative fuels like electric vehicles are getting more popular due to less emissions.

5 Types of Fuels for Cars or Automobiles

So let’s see the fuel used in automobile vehicles one by one.

Types of Fuels used in automobile vehicles

  • Petrol
  • Diesel
  • Compressed natural gas or CNG
  • Liquified petroleum gas or LPG
  • Ethanol

These are the well-known automobile fuels available right now in the market. The gasoline and diesel are common whereas the CNG and LPG use is increasing with its advancements.

Let’s see each of them in detail.

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Fuel Types Gasoline (Petrol)

The gasoline is used as fuel in automobile vehicles from long time. It is used in all spark ignition-based automobile engine vehicles.

  • Gasoline is acquired from the crude oil fractional distillation process.
  • If we consider, 160 liters or 42 US gallon barrel of crude oil is extracted, the gasoline from this much amount of crude oil acquired is 72 liters (19 US gallons).
  • The quality of the petrol fuel is measured in terms known as octane rating.
  • Some type of gasoline tends to increase the knocking and detonation problems in engines.
  • Lots of additives are added later to get the good quality of gasoline fuel.
fuel types gasoline petrol
Fuel types gasoline petrol

The evolution of the gasoline engines began in the world war one. Colonies like Britain and Germany were constantly trying to improve their Navy and the coal fuel was the only fuel used in the ships those times.

The gasoline was just a byproduct of the crude oils and the crude oils were mainly used to produce the kerosene.

  • In world war 1 gasoline fuels with higher compressions ratios didn’t give satisfactory performance due to abnormal combustion problems.
  • Later with the advancements and research in gasoline.
  • They were extensively used in world war 2.
  • In the 1950s factories started to focus on high octane fuels by adding additives to the gasoline.

Octane Rating

 An octane rating or number is like a standard for measuring the performance of an engine.

The higher the compression ratio higher will be the compression capability of fuel before detonating.

  • In simple words, the higher the octane rating the performance of the gasoline will be better.
  • High octane-rated gasoline engines are used in high-performance engines.
  • When the air-fuel mixture is supplied the spark will ignite the mixture causing the combustion and piston will move and the engine will start to work.
  • But if the fuel is getting into combustion already before sparking then the abnormal combustion might damage the engines.
  • This is where the octane rating comes into play.

The higher-octane rating means the fuel will not get into premature combustion. It will resist even at higher temperatures and compression.

The octane rating differs country wise. The octane rating mostly used is research octane number (RON). The RON-87 is the most widely used octane rated gasoline fuel.

As the scale goes up the use of gasoline goes for premium and high-performance cars. Like, in the United Kingdom the mostly used fuel has 95 RON number.

Additives used in Gasoline


To counter the knock and detonation problems in the gasoline engines the Tetraethylead is used.

It was extensively used in gasoline engines during the 1920s. But later due to the harmful effects of lead it was phased out.

Methylcyclopentadienyl manganese tricarbonyl (MMT)

The MMT is mostly used in Canada and USA to boost the octane rating.

Antioxidants and metal deactivators

In the long-term storage of gasoline, the sticky and gummy deposits and formed due to oxidation.

  • The degradation is avoided with the use of antioxidants like phenylenediamines and other amines.
  • Gums formed are accelerated due to the copper salts, so to neutralize this the metal deactivators are used.
  • These deactivators will deactivate the metal salts promoting the growth of gummy residues.


To reduce the carbon build-ups and allowing the easier starting of engines in cold environments the detergents are used.

Alkylamines and alkyl phosphates are used as detergents.

Advantages of Gasoline fuels

The advantages of gasoline fuels shall be as follows,

  • Easy to transport and it is relatively inexpensive.
  • Gasoline is common fuel and it is available everywhere easily.
  • Starts up immediately, because gasoline is highly combustible.
  • Produce less noise as compared to diesel engines.
  • Longer lifespan of the engine

Disadvantages of Gasoline fuels

The disadvantages of gasoline fuels shall be as follows,

  • Gasoline is extremely flammable.
  • Relatively costly compared to diesel engines.
  • High carbon pollution
  • Price fluctuations due to supply and demand

Types of Fuels Diesel

The diesel fuel is different from the petrol fuel. The spark is given in case of the gasoline powered engines. But in case of diesel engine are ignited without any need of spark plug.

  • Diesel engines are mostly used in heavy vehicles and preferred due to its high thermodynamic efficiency and fuel efficiency.
  • A German scientist Rodolph Diesel conducted experiments on the compression ignition engines in 1892.
  • Diesel was not much of used compared to petrol and kerosene in the early years.

Diesel fuel is produced from various sources, mostly it is produced from petroleum. Other sources like biomass, animal fat, etc.

Diesel fuel has three types let’s see each one of them.

Petroleum diesel

Petroleum diesel is produced from the fractional distillation process of crude oil.

Fractional distillation is done at the temperature of 200 degrees Celsius to 350 degrees Celsius.

It is also known as the Petro diesel or fossil diesel.

Synthetic fuel

Synthetic fuel is produced from carbon materials like biomass, biogas, natural gas, and coal.

The raw material from these materials is gasified to synthetic gas first and then they are converted by the Fischer-Tropsch process to synthetic diesel.


The bio-diesel is acquired from the vegetable oils and animal fats. It is produced from lots of various oils like rapeseed oil or soyabean oil.

  • But the fuel equipment manufacturers raised concerns over the use of bio-diesel over the problems of fuel injection components corrosion, low-pressure fuel system blockage, etc.
  • But the bio-diesel produced less pollution emitting gases.
  • Sulfur, sulfur di-oxides which are major components and responsible for acid rain they emitted in less numbers from the bio-diesel.

Cetane number of Diesels

The gasoline fuels have their performance rated according to the octane number. Similarly, diesel fuels are rated according to the cetane number.

  • Cetane number shows the speed of diesel fuel and compression needed for ignition.
  • In brief, the higher the cetane number the diesel fuel will have a shorter ignition delay.
  • Higher cetane number fuels are equipped with lots of additives to improve the numbers.
  • The standard or working diesel fuel range is 42 to 50 cetane number.
  • To improve the cetane number Alkyl nitrates and di-tert-butyl peroxide are used as additives.

Advantages of Diesel Fuels

The advantages of diesel fuels shall be as follows,

  • Low flammability so less dangerous fuel
  • Easy availability
  • Relatively cheaper than the gasoline engines
  • High thermal efficiency and fuel efficiency
  • More durable vehicles

Disadvantages of Diesel Fuels

The disadvantages of diesel fuels shall be as follows,

  • Diesel vehicles usually cost more.
  • More repair cost and needs scheduled maintenance
  • Stronger engine but less vehicle speed
  • Diesel engines make more noise than petrol engines

Compressed Natural Gas Fuel Types

Compressed natural gas known as CNG is alternative fuel that can be used in place of petrol or diesel. It is preferred because of low pollutants emissions.

  • Also, natural gas has less threat in case of spilling.
  • Compressed natural gas is primarily made from methane (CH4) gas.
  • The energy is created by the combustion of methane CH4 gas. CNG is used in traditional petrol diesel engines as well as can be used alone.

Sometimes it is also used with gasoline or diesel engines known as bi-fuel. The use of CNG is rapidly increasing in Asian countries like India, Iran.

The rising gasoline prices are the main reason for the increasing use of compressed natural gas as fuel. Also, the environmental benefits are more compared to popular fuels.

  • CNG is stored at almost 3000 to 3600 pounds of pressure.
  • The storage tank requirement is massive and costly than the usual conventional tank.
  • Also, the time required for refueling depends on the refueling stations. Some stations have slow speed refueling of about 0.4 GGE/hr, fast stations provide 10 GGE in just 5-10 minutes.
  • The CNG stations availability is rapidly increasing but still it’s not the same as the petrol and diesel fuels availability.

The CNG’s are now used in motor vehicles, locomotives. Manufacturers like Fiat, Toyota, Honda, Volkswagen are selling bi-fuel cars.

Advantages of CNG vehicle

The advantages of CNG vehicles shall be as follows,

  • The CNG-powered vehicles need lower maintenance costs compared to other hydrocarbon-fueled vehicles.
  • These systems are sealed, there is less chance of spills or evaporation of the gas.
  • CNG mixes well with the air as CNG is also gas.
  • CNG emits significantly less pollution emissions compared to gasoline and diesel. Switching to CNG can help to reduce greenhouse gases.
  • CNG vehicles are considered safe than gasoline-powered vehicles.

Disadvantages of CNG Vehicles

The disadvantages of CNG vehicles shall be as follows,

  • Needs more space for fuel storage compared to gasoline storage.
  • Unburned methane if leaked, its most harmful component contributing to greenhouse gases.
  • Higher installation costs.
  • Low performance compared to gasoline and diesel engines.

Types of Fuels Liquified Petroleum Gas

The liquified petroleum gas is a mixture of propane and butane gas. It is widely spreading as a green fuel because of low carbon dioxide emissions compared to petrol.

Just like the compressed natural gas, the liquified petroleum gas can be used alongside gasoline as a bi-fuel arrangement.

  • LPG is also known as the Autogas.
  • The vehicles with Autogas and gasoline can be switched to desired fuel during the operation.
  • LPG is the third most popular fuel having 3% of the market share in the world.

In the United states the LPG is known as propane Autogas. In the most of the Asian countries the term LPG is used instead of Autogas.

  • The LPG use is popular among taxis, auto-rickshaws, etc.
  • The major drawback of LPG is the unavailability in remote areas.
  • To avoid the issue of availability some manufacturers use bi-fuels in their vehicles that runs on gasoline as well as Autogas.

Let’s see some advantages and disadvantages of the LPG as a fuel in automobiles.

Advantages of LPS Gas

The advantages of LPG gas shall be as follows,

  • LPG has good anti-knocking properties and mix-up with air at any temperature.
  • LPG is non-toxic and non-corrosive gas.
  • LPG emits low content of carbon compared to petrol fuel.
  • No carbon deposits are made on a spark plug that increases the life of the spark plug.
  • The LPG-powered vehicles are nearly smoke-free and efficient.
  • Low contribution to the greenhouse gases.

Disadvantages of LPG Gas

The disadvantages of LPG gas shall be as follows,

  • In underdeveloped markets, refueling stations are a major problem.
  • Risk of explosion and irregular supply.
  • The storage tank is heavy and LPG has low energy density.
  • LPG is heavier than air, because of this reason it gets collected at the lowest spot and if any leakage happens it is more hazardous in case of fire.
  • Engine starting troubles due to low vapor pressures.

Types of Fuels Ethanol

The ethanol fuel is ethyl alcohol, it is the same type which is found in the beverages. It can be used as fuel and mostly used as a motor fuel.

  • Fiat 147 was the first car running on ethanol fuel in 1978.
  • Ethanol nowadays is mostly used as an additive in gasoline fuel.
  • It is made from the catalytic hydration of ethylene.
  • Apart from ethylene, it is acquired from acetylene, calcium carbide, coal, oil gas, etc.

Ethanol is mainly produced by three methods, fermentation, distillation and dehydration. The fermentation of sugar which is a microbial fermentation is used to produce ethanol.

  • The major source for fermentation is sugar cane.
  • The sugar cane factories have the separate area for the fermentation of sugar cane to obtain the ethanol (ethyl alcohol).
  • After the fermentation process the solids and water are removed by the distillation process.

Mostly the ethanol only used as an additive for gasoline-powered vehicles. Let’s know some advantages and disadvantages of ethanol fuel.

Advantages of Ethanol

The advantages of ethanol shall be as follows,

  • Ethanol is cost-effective compared to other biofuel alternatives. Almost every country can produce the ethanol from corn, sugar cane etc.
  • Environmentally friendly, ethanol compared to other fuel sources produced low pollution. On combustion it gives out low levels of toxic gases.
  • Less contribution to global warming, ethanol unlike other gases doesn’t emits dangerous greenhouse gases.
  •  It can be easily made from sugar cane, corn like plants. The availability is more and also helps to minimize the dependency on the fossil fuels.
  • Ethanol can be great help to agricultural sector. As the ethanol depends on agricultural production, it can help the agriculture sector to uplift.

Disadvantages of Ethanol

The disadvantages of ethanol shall be as follows,

  • Large lands required with the plantation of sugar canes and corns etc. To meet the demand large land area with ethanol-producing plants needs to be covered.
  • Ethanol has high water retention capabilities; it is difficult to get the purest form of ethanol.
  • Though ethanol doesn’t produce greenhouse gases, the production of ethanol in processes like distillation needs heat and it is acquired from fossil fuels.
  • The disposal of waste products of fermentation is a major problem.

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One thought on “What is Fuel? Definition, Types of Fuels – Petrol, Diesel, CNG, LPG, Ethanol for Cars

  1. It’s great that you talked about how there are lots of fuels used in automobiles at this time. I’ve owned our car for quite a while now and I think it is time for us to switch to a new type of fuel. With that in mind, I should probably stop by a gas station later and see what type of fuel is available.


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