Monday, 8 January 2018

Difference Between Petrol and Diesel

Petrol and Diesel are the liquid mixtures used as a fuel. Both are derived from the crude oil or petroleum products. Basically, these are hydrocarbons presents in the crude oil but having difference in the properties. The method used to derive petrol as well as diesel is same and called as ‘Fractional distillation’. These hydrocarbons are extracted from the crude oil based on the difference in their boiling points.


Petrol is a mixture of alkanes and Cycloalkanes generally derived by distillation of the crude oil. It has the length of the carbon atom chain ranges from 5 to 12. It is also known as gasoline and usually used in the internal combustion engine to give more speed to the engine. It is lighter and highly volatile liquid tends to makes less pollution.


Diesel is made up of alkanes and generally the carbon chain of it contains about 12 atoms. It is heavy and less volatile liquid having more viscosity. It is most suitable fuel for motor vehicle. It is safe to store as well as transport and usually used in CI engine.

Difference between Petrol and Diesel:

Petrol and diesel can be differentiate into following aspects. 

Difference Between Petrol and Diesel

Chemical Composition:

Petrol is basically a mixture from  7 (n-Heptane) or 8 (2,2,4-trimethylpentane) and Diesel has a mixture which has carbon chain from  8 (n-octane) to 21 (undodecane).

Chemical formula of the Petrol is C8H18 and Diesel has the chemical formula C12H23.

CO2 emission by the Fuel:

Diesel produces more CO2  than petrol. Diesel contains the higher proportion of the carbon atoms hence it produces about 13% more CO2 than petrol.

Energy content:

Diesel is denser fuel as compare to the petrol hence has more energy content than petrol. Petrol has the energy content of about 33.7 MJ/kg and it is approximately 36.7 MJ/kg in case of Diesel. Finally it can be said that diesel has around 16% more energy content than petrol.


Petrol has less viscosity as compare to the Diesel. It can be increased at the lower temperature in case of Diesel but there will be no any change observed in case of petrol.


Petrol has types of additives and constituents which are responsible to make it more volatile therefore Volatility of the petrol is greater compared to the diesel.

Boiling ranges:

Boiling point of the petrol is lower than diesel. For the petrol it ranges between 350 degree C to 2000 degree C and it ranges 1800 degree C to 3600 degree C in case of the Diesel.

Fuel economy:

Petrol has lower fuel economy than Diesel and it can be seen better fuel economy for the Diesel.


Power of the Diesel fuel is higher than petrol. Petrol has the power of 34.6 mega joules per litre and diesel contains about 38.6 mega joules per litre. The petrol engine always runs at the higher RPM and Diesel engine requires more torque to run well.


It is always a dangerous practice to store the greater amount of the fuel which tend to be flammable and hazardous. Petrol is a greatly flammable fuel as compare to the Diesel due to high vapor pressure. Diesel is a less flammable fuel due to low vapor pressure, and it is easier to obtain during the requirements in disaster.

Types of ignition:

The Auto-ignition temperature of the petrol is 2460 degree C, and it requires Spark Plug for the sufficient ignition of the mixture of air and fuel.
Diesel has auto ignition temperature of around the 2100 degree C and Spark plug is not necessary for the ignition of the fuel. It simply works on the method of compression. The mixture of air and fuel get compressed with the help of high pressure which alternative increases the temperature of the mixture and helps it to ignite.

Calorific value:

The net calorific value of the Petrol fuel is about 44.4 MJ/kg and the calorific value of the diesel is around 43.4 MJ/kg

Flash point and fire point:

Flash point referred as the minimum temperature at which fuel gets available for ignition in the evaporated state. Flash point of the petrol is 430 degree C, and it is the 520-950 degree C for Diesel.
Fire point is the temperature at which vapor of the fuel tends to burn for the minimum five second. The fire point of petrol as well as Diesel is higher by 10 degree then flash point.

Octane and cetane rating:

Petrol is indexed by Octane number and generally it is the ability to resist auto ignition when used in the gasoline engine. It is used to measure the octane rating of the Petrol.
All the diesel engine is rated under the Cetane number. It measures how quickly the fuel start to burn inside the compressor. Combustion speed of the Diesel is depends upon the Cetane number


Diesel is cheaper than Petrol due to its availability compare to petrol.

These are all key differences between petrol and diesel. If you have any query regarding this article, ask by commenting. If you like this article, don't forget to share on social network with your friends. Subscribe our website for more informative articles. Thanks for reading it.


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