Difference Between Petrol and Diesel Engine [With PDF]

Hello readers, welcome to India’s Most Trusted Mechanical Blog.

I am Amrit, and today I am going to discuss what are the differences between the petrol engine vs Diesel Engine. And how you can defer this in technical terms. So let me first tell you a little about Petrol and Diesel Engine.

So what is a Petrol Engine?

As the name suggests “Petrol”, you make a simple definition of a Petrol engine like an engine where we use petrol as fuel to produce power is called a petrol engine.

Generally, Petrol Engines are called SI Engine. The full form of SI is Spark Ignition.

We need a spark plug to burned or ignite the petrol, that’s why it is called the spark-ignition engine.

Now talking about Diesel Engine:

An engine is called diesel engines where we use diesel as fuel to produce the power.

Diesel Engines are called CI Engine, which means the Compression Ignition engine.

In the case of Diesel Engine only air is sucked in the suction stroke and then air is compressed to very high temperature and pressure, and then an injector sprayed the atomized diesel inside the compressed air, and in a second the fuel is burned and generate power. As the ignition is happened by the compression of air, that’s why this type of engine is called a compression ignition engine.

So now you have the idea about the Diesel Engine and Petrol Engine, now dive into the differences.

Difference Between Petrol and Diesel Engine:

Difference Between Petrol and Diesel Engine
The Petrol engine works on the principle of the Otto cycle.The Diesel engine works on the principle of the Diesel cycle.
In Petrol engine carburetor is fitted with the cylinder.In Diesel engine carburetor is not fitted with the cylinder. Instead of a carburetor, we use a fuel injector and fuel pump to supply the diesel.
Both Air and fuel mixture is drawn into the cylinder in the petrol engine.Only air is drawn into the cylinder in the diesel engine.
In Petrol Engine Spark Plug is fitted with the cylinder.In the Diesel engine, the Fuel Injector is fitted with the cylinder.
The compression ratio petrol engine is generally 7:1.In case of a diesel engine, the compression ration is 16:1.
In the petrol engine, less power is developed.Here in diesel engine more power is developed.
The construction of flywheel is light.In this case, the flywheel construction is heavy.
The petrol engine is used for lighter vehicles. The Diesel engine is used for heavier vehicles.
In Petrol Engine Battery is essential for generating the spark.In Diesel, engine Battery is essential for an only lighting purpose.
Maintenance cost is higher for Petrol Engine The maintenance cost is low in the Diesel engine.
Due to the lower compression ratio the size of the petrol engine is small.Due to achieving the higher compression ratio the size of the diesel engine is bulky.

Here are some extra resources you may check out:

Four-Stroke Petrol & Diesel Engine
Two-Stroke Petrol & Diesel Engine
Difference between SI and CI Engines
Difference between Spark Plug and Fuel Injector

Here is a cool video by Car Throttle:

So this is all about the Diesel Engine vs Petrol Engine. I hope you liked the way I present.

However, we also have plenty more lessons on Mechanical. Do check it out.

Till then Goodbye, see you in another article.


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Anup Kumar Dey

A Mechanical Engineer with 19 years of working experience in various renowned MNCs.

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