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.
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 Engine||Four Stroke Petrol Engine|
|1||The 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.|
|2||It works on Diesel Cycle.||It works on Petrol or Otto Cycle.|
|3||In this engine, Diesel is used as fuel.||In this engine, Petrol (gasoline) or CNG is used as Fuel.|
|4||The fuel injector initiates the combustion.||Spark Plug generates a spark to ignite the charge.|
|5||Fuel 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.|
|6||It requires a high-pressure fuel injection system.||The high-pressure fuel injection system is not necessary.|
|7||These engines produce more torque.||It produces comparatively lower torque.|
|8||It runs at a lower RPM.||It runs at a comparatively higher RPM.|
|9||The fuel used is less volatile.||It uses more volatile fuel.|
|10||Lower 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.|
|12||It has a more rigid design because of the higher compression ratio.||These engines are less rigid than four-stroke diesel engines.|
|13||These engines last longer than petrol engines.||It has a lower lifespan than four-stroke diesel engines.|
|14||Less fuel consumption as the fuel used is higher dense.||More fuel consumption as compared to Four Stroke Diesel engines.|
|15||The initial cost of Four Stroke Diesel Engine is High.||It has a lower initial cost.|
|16||More maintenance costs as it uses costly components.||Less maintenance cost.|
|17||It 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.|
|18||Difficult to a cold start.||Cold starting is easier than the four-stroke diesel engines.|
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.
Is four-stroke diesel engines cheap than petrol engines?
No, four-stroke diesel engines are more expensive than four-stroke petrol engines.