Greenhouse Travels

Physics homework!?
I have this question I’m not too sure about. It says that out of a smart car weighing 730kg, a car weighing 1275kg and a car weighing 1785kg which one would contribute the least amount of greenhouse gases when travelling the exact same route?
I’m thinking it’s the smart car because it has a smaller mass therefore will not need as much fuel to convert to energy and therefore will not produce as much greenhouse gases as the larger cars. Does this sound right? and does anyone have any other ideas?
i would agree that its the smart car but the first thing that pops in my mind is the term “smart” car in my openion infering a car designed with features to improve effeciencies and environmentally friendly.
Additionally the reasoning with the mass also sounds logical.
Travel to the Irish National Botanic Gardens