Four words have been given out of which three are alike in some manner, while one is different. Choose the odd one.

Petrol

THE LOGIC;

The similarity among the first three (Bus, Car, and Aeroplane) is that they are all modes of transportation or vehicles.

They are means of traveling from one place to another.

On the other hand, "Petrol" is differen,  it is a type of fuel used to power vehicles like cars and buses, as well as aeroplanes.

It is not a mode of transportation itself, making it the odd one out in the given set.