All of us know density decreases with increases in temperature and vice versa.

A simple application of it-
It is advisable to refuel engine in night or early morning. Since the temperature will be lesser at night compared to day time density of fuel will be higher (at night than at normal day). So amount(mass) of fuel into the engine will be greater at night. Ex You are trying to fill 1 litre of fuel(ρ=m/v=> m=ρ*v). Since density is greater at night,volume being constant(1 litre) amount of fuel into engine will be greater at night. Greater the fuel more the efficency and performance. Therefore it is advisable to refuel at night.