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  /  General   /  Difference Between Petrol Engine and Diesel Engine

Difference Between Petrol Engine and Diesel Engine

Difference Between Petrol Engine and Diesel Engine
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In theory, petrol and diesel are quite similar. Petrol (i.e., gasoline) and diesel are both created from fractional distillation of petroleum from crude oil. One cannot mix or interchange Petrol and Diesel together as they have different chemical chains and other differences. Let’s look at a few fundamental differences between the two:


Crude oil can be used to make different fuels depending on its consistency and is categorised into lighter and heavier components. The lighter portion is used to make Petrol which is why it has a lighter consistency. Diesel is made using the thicker portion, therefore, has a denser and an oily consistency.


Petrol is removed from crude oil at a temperature of 40°C to 205°C whereas Diesel is produced by conducting a distillation process on crude oil between 200 °C (392 °F) and 350 °C (662 °F) at atmospheric pressure.


If your car travel is not very substantial, then you can go for petrol. For longer and more frequent runs (like commercial carriers) diesel is a better option. As a rule of thumb if your total run doesn’t exceed 500km a month then you need to opt for petrol variant, otherwise get a vehicle with a diesel engine.


Aside from chemical difference, petrol and diesel differ in how they are burned. Because Petrol has a low compression ratio, it utilises a spark plug to ignite the fuel, but Diesel doesn’t because it has a higher compression ratio.

Petrol engine:

A mixture of petrol and air is forced into the cylinder and is compressed. The mixture is ignited using a spark plug and made to explode which forces the piston up and gives your car the required power. The burned mixture is then forced out of the car as an exhaust.

Diesel engine:

Air is compressed inside a cylinder while diesel fuel is sprayed into it. The compression causes the diesel fuel to ignite, which pushes the piston upwards supplying the car with energy. The remaining burnt mixture comes out of the car as exhaust.


Diesel fuel does not contain any lead and emissions from regulated pollutants such as carbon monoxide and nitrogen oxide. However, diesel does create higher emissions of nitrogen oxides and particulate matter as compared to petrol cars, which are considered carcinogenic. Despite the fact that diesel provides better fuel economy, petrol burns cleaner than diesel; precisely the reason why diesel cars lack behind petrol cars in terms of usage.

To conclude

Both Petrol and Diesel come with their advantages and disadvantages. Even though diesel has more fuel efficiency and mileage than petrol, it’s costlier and often requires repairs which can be expensive. Hence, the better choice between the two fuels depends on the requirements and needs of the buyer as the differences between both the fuels are constantly evolving.


Read more on Which is better? Petrol Vs Diesel Car.

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