About Petrol and Diesel Engines

How can you differentiate a petrol or gasoline engines from a diesel engine, below are some basic facts about these engines.

Basic facts about Petrol and Diesel Engines

Engine that uses no spark plugs are diesel engines. Diesel engines do not require a spark for internal combustion to occur because they are compression ignition engines. Diesel can self-ignite under high compression, temperature and pressure within the combustion chamber of the engine.

Petrol engines are spark ignition engines. Petrol can’t self-ignite within the combustion chamber, it still needs a spark for internal combustion to occur.

Difference between Petrol and Diesel Engines.


The diesel engines have bigger cylinder volumes compared to petrol engines of the same size. Hence diesel engines have higher compression ratios making them more efficient than petrol engines. The compression ratio of a diesel engine is higher than that of a petrol by 2 to 1.


Diesel engines make louder noise than petrol engines.

Engine Size

In terms of engine size, diesel engines are bigger. Most big engines runs on diesel fuel. Note that most car engines run on petrol because the engine size are smaller while bigger vehicles such as trailers, lorries, bulldozers etc. runs on diesel.

Spark plugs

Petrol engine have spark plugs fitted, will sparks plugs are absent in a diesel. This is one way you can easily identify a petrol engine from a diesel engine.

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