Difference Between Petrol and Diesel Engines

Petrol and diesel engines are the two most common types of internal combustion engines. Diesel engines are used to power heavy machinery and vehicles such as heavy-duty trucks, buses, trains, and boats. Petrol engines are common with smaller cars, small electricity generators, lawn mowers, chainsaws, etc. 

This article explains the different operational mechanisms of both engines and why diesel engines are common with heavy-duty trucks and large machinery.

Diesel Versus Petrol Engines—How They Operate

As their names suggest, diesel engines run on diesel, while petrol engines use petrol (gasoline) fuel. Both engine types have one objective; to burn fuel and convert it into mechanical energy. However, their only difference is how they ignite the compressed air-fuel mixture in the combustion chambers.

Petrol engines use spark plugs to ignite the compressed air-fuel mixture in the combustion chamber. The spark plugs are connected to the ignition system, which provides the sparks. While most petrol engines have one spark plug per cylinder, some have two to provide more efficient fuel combustion.

Diesel engines do not require spark plugs to operate. They use a different type of ignition called compression ignition. The piston compresses the air inside the cylinder, increasing both pressure and temperature. Fuel is then injected into the cylinder, causing an ignition since the temperature is already high.

Diesel engines are more efficient since they operate at higher compression ratios. This is because the fuel is compressed to a greater extent, which increases the efficiency of the engine. A higher compression ratio means a higher percentage of energy is extracted from the fuel. They are also more durable and require less maintenance than petrol engines. They also produce fewer emissions.

Why Diesel Engines are used in Trucks and Heavy-duty Machinery

Trucks and heavy-duty machinery require powerful engines to carry heavy loads. As compared to a petrol engine, a diesel engine produces more torque since it has a higher compression ratio. High torque is what is required by trucks and heavy-duty machinery to do the heavy work.