Difference between 4 stroke petrol and diesel engine [with Pdf]

The basic difference between these two engines is that the four stroke petrol engines use a spark plug for the ignition while the four stroke diesel engine uses a higher compression ratio so that the fuel can undergo auto-ignition.

Difference between 4 stroke petrol and diesel engine

Four stroke petrol engine:

These are the spark ignition (SI) engines that work on a principle of the otto cycle. In these engines, the fuel is mixed with air before it reaches the combustion chamber.

In this, the air-fuel mixture is ignited by the generation of a spark with the help of a spark plug. As it does not work on autoignition, these engines work at a lower compression ratio.

These engines can be noticed mostly in light-duty applications like cars, two-wheelers, smaller generators, ATVs, etc.

Four stroke diesel engine:

These are the compressed ignition engines that work on the diesel cycle. In these engines, the air is compressed at high pressure to reach the auto-ignition temperature of the diesel, and then the fuel is spread in the hot air with the help of a fuel injector.

As the fuel is directly injected into the pressurized air in the combustion chamber, it requires a high-pressure fuel injection system.

These engines are used in heavy-duty applications like trucks, tractors, Diesel generators, cargo ships, etc.

Difference between four stroke petrol and diesel engine:

Sr. No.Four Stroke Diesel EngineFour Stroke Petrol Engine
1The higher compression ratio helps for the auto-ignition of the fuel.In this engine, Combustion starts due to the generation of a spark in the Air-Fuel Mixture.
2It works on Diesel Cycle.It works on Petrol or Otto Cycle.
3In this engine, Diesel is used as fuel.In this engine, Petrol (gasoline) or CNG is used as Fuel.
4The fuel injector initiates the combustion.Spark Plug generates a spark to ignite the charge.
5Fuel mixes with air inside the combustion chamber.Fuel mixes with air in the carburettor or in the intake manifold before going to the combustion chamber.
6It requires a high-pressure fuel injection system.The high-pressure fuel injection system is not necessary.
7These engines produce more torque.It produces comparatively lower torque.
8It runs at a lower RPM.It runs at a comparatively higher RPM.
9The fuel used is less volatile.It uses more volatile fuel.
10Lower wear of cylinder due to the lubricating properties of diesel.The gasoline can wear the engine components faster.
11 The compression Ratio is High.It works at a lower compression ratio.
12It has a more rigid design because of the higher compression ratio.These engines are less rigid than four-stroke diesel engines.
13These engines last longer than petrol engines.It has a lower lifespan than four-stroke diesel engines.
14Less fuel consumption as the fuel used is higher dense.More fuel consumption as compared to Four Stroke Diesel engines.
15The initial cost of Four Stroke Diesel Engine is High.It has a lower initial cost.
16More maintenance costs as it uses costly components.Less maintenance cost.
17It is used in heavy-duty applications like buses, trucks, farm tractors, etc.It is used in light-duty vehicles like two-wheeler, cars, ATVs, etc.
18Difficult to a cold start.Cold starting is easier than the four-stroke diesel engines.

FAQs:

  1. Which engine has a higher life expectancy, a four-stroke petrol engine or a four-stroke diesel engine?

    The four-stroke diesel engines last longer than petrol engines because of their more rigid structure.

  2. Is four-stroke diesel engines cheap than petrol engines?

    No, four-stroke diesel engines are more expensive than four-stroke petrol engines.

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