Density

The density of gasoline is 0.71–0.77 kg/l (0.71–0.77 g/cm3),(in English units, approx. 0.026 lb/cu in or 6.073 lb/U.S. gal or 7.29 lb/imp gal) which means it floats on water. This may be advantageous in the event of a spill. It is flammable and can burn while floating over water.
As an example, 65l of mogas (the maximum allowed in microlight aircraft in some countries) weighs about 50kg. This is a significant proportion of the payload: an Ikarus C42 has an empty weight of 270kg, so with full fuel the passenger(s) and any baggage must total no more than 130kg (290 lb).