The difference between a petrol engine and a diesel engine are
Petrol Engine
(i) In the intake stroke of a petrol engine, a mixture of petrol vapour and air enters into the cylinder.
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(ii) Petrol engine has a spark plug. In a petrol engine, the combustion of petrol vapour takes place due to the heat of the spark provided by the spark plug.
(iii) In a petrol engine, the mixture of petrol vapour and air is compressed to about 1/8 part of its original volume.
(iv) The efficiency of a petrol engine is comparatively less.
(v) The petrol engine is comparatively light and cheaper,
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(vi) Due to the higher price of petrol, the use of a Petrol engine is more expensive.
Diesel Engine
(i) In the intake stroke of a diesel engine, only air enters into the cylinder.
(ii) There is no spark plug in the diesel engine. The combustion of diesel oil takes place due to the heat produced by the excessive compression air in the cylinder.
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(iii) In a diesel engine, the air is compressed to about 1/16 part of its original volume.
(iv) The efficiency of a diesel engine is more than that of a petrol engine,
(v) The diesel engine is comparatively heavy and costlier.
(vi) Due to the lower price of diesel, the use of a diesel engine is comparatively cheaper.