Difference Between Petrol And Diesel

Another curious question, In this article, we will talk about the difference between the two most commonly used fuel Petrol or Gasoline and Diesel.

Petrol and Diesel are used as fuel in IC and CI engines. It is obtained by fractional distillation of crude oil. When crude oil is heated first, LPG gas vaporizes then petrol is obtained. Petrol is a hydrocarbon which contains 4-12 carbon-carbon atoms per molecule. The common molecules found are alkanes, cycloalkanes, aromatic chains, and asphaltenes. These alkanes also are known as paraffin have the chemical formula CnH2n+2.


The alkane from pentane to octane (C5H12-C8H18) is refined to petrol while the alkane from nonane to hexadecane (C9H20-C16H34) is refined as diesel or kerosene. Diesel fuel is used in compression ignition engines while petrol (or also called gasoline) is used in spark-ignition engines.

Also Read:Pros and Cons – diesel engine vs. petrol engine

Difference between the two:




Chemical name Mostly cyclic compounds like aromatics and naphthalene Straight chain of hydrocarbons
Chemical formula Ranges from C5H12-C8H18 Ranges from C9H20-C16H34
Energy content Less compared to diesel as it is lighter.

Energy content is 33.7MJ/Kg

Up to 16% more energy content than petrol as it is denser.

Energy content is 36.7MJ/Kg

CO2 emission Less proportion of carbon atoms so less CO2 emission More proportion of carbon atoms so more CO2 emission
Engines Spark-ignition engine Compression ignition engine
Viscosity Less viscous More as compared to petrol
Volatility Greater because of the additives Less volatile
Boiling temperature 350oC-2000oC 1800oC-3600oC
Power 34.6MJ/ltr

Higher RPM for petrol engines


More torque in case of diesel engines

Calorific value Net calorific value=44.4MJ/kg Net calorific value=43.4MJ/kg
Flammability Has high vapor pressure. Hence more flammable Has less vapor pressure so less flammable
Ignition type Self-ignition temperature is  2460oC

For combustion of this fuel, the spark plug is required

Self-ignition temperature is  2100oC

Self-ignited because of temperature rise due to high-pressure compression.

Flashpoint (the minimum temperature at which fuel is available for ignition in the evaporated  state) 430oC Ranges from 520oC-950oC
Fire point(temperature at which fuel tends to burn itself and stays for five seconds) Near about 440oC 530oC-960oC
Indexing By octane number, it is the ability to resist auto-ignition. By cetane number, combustion speed depends on this number
Fuel price Price is more Price is less

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  1. Chris Gilmore March 31, 2018
  2. muzammal April 5, 2018

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