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 nameMostly cyclic compounds like aromatics and naphthaleneStraight chain of hydrocarbons
Chemical formulaRanges from C5H12-C8H18Ranges from C9H20-C16H34
Energy contentLess 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 emissionLess proportion of carbon atoms so less CO2 emissionMore proportion of carbon atoms so more CO2 emission
EnginesSpark-ignition engineCompression ignition engine
ViscosityLess viscousMore as compared to petrol
VolatilityGreater because of the additivesLess volatile
Boiling temperature350oC-2000oC1800oC-3600oC

Higher RPM for petrol engines


More torque in case of diesel engines

Calorific valueNet calorific value=44.4MJ/kgNet calorific value=43.4MJ/kg
FlammabilityHas high vapor pressure. Hence more flammableHas less vapor pressure so less flammable
Ignition typeSelf-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)430oCRanges from 520oC-950oC
Fire point(temperature at which fuel tends to burn itself and stays for five seconds)Near about 440oC530oC-960oC
IndexingBy octane number, it is the ability to resist auto-ignition.By cetane number, combustion speed depends on this number
Fuel pricePrice is morePrice is less

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