Question

Why petrol is used for light vehicle, and diesel for heavy vehicle

Answer 1

There are quite a few reasons I could think of:

i. Diesel, as a fuel, has slower combustion characteristics as compared to petrol. So, for a given power, they produce higher torque at low speeds, which is the primary requirement of a heavy engine.

ii. Diesel engines employ higher compression ratios; so the peak pressures and temperatures reached are higher as compared to petrol engines, which in turn requires the engines to be heavy and robust.

iii. Also, for the same maximum pressure and temperature, the efficiency of a theoretical Diesel cycle is higher as compared to the Otto cycle.

iv. If we try to use petrol in bigger-sizedengines, it might lead to too much of knocking (because of their pre-ignition