Why heavy vehicles including locomotives are always fitted with diesel engines?
Why can’t they have petrol engines?
We should remember that petrol is highly combustible than diesel. In comparison to diesel, petrol burns fast and provides quick energy. This makes petrol unsuitable for heavy vehicles. Burning of petrol provides lots of energy in a short period of time. At this circumstance, the vehicle using petrol as fuel has to move fast for best use of energy generated by the engine.
But the heavy vehicles like buses, trucks or diesel locomotives transport heavy load. Because of it they cannot travel fast. This may lead to a situation in which the cylinder of petrol using vehicle may burst. So, it is warned not to overload cars with petrol engines. In contrast, the heavy vehicles have large cylinders as they consume fuel in large amount. Diesel burns slow in comparison to petrol, so it is more suitable for heavy vehicles.
Heavy vehicles require more energy at low speed. Diesel engine can provide high torque than petrol engine hence diesel engine is preferred for heavy vehicles. The fuel efficiency of diesel engine is high as compared to the petrol engine because diesel burns at a slow rate in comparison to petrol at moderate temperature because of the chemical composition of diesel.