Petrol (gasoline to Americans) is dangerous largely for is vapours. It's one of the lightest-possible liquid fuels with about 6 carbon atoms per molecule (C6).

Petrol (gasoline to Americans) is dangerous largely for is vapours. It's one of the lightest-possible liquid fuels with about 6 carbon atoms per molecule (C6).[1] Most ships don't burn petrol itself,[2] but rather heavier fractions of petroleum, generally either diesel (~C16) or bunker fuel (~30 or longer), which don't vapourise readily. It's possible to extinguish a lit match in diesel fuel (the vapours above petrol would ignite and/or explode), and bunker fuel generally won't even flow until it's been heated above the boiling point of water (spent steam from steamships is used to heat the incoming fuel both so that it will flow and to vapourise it before injection into boilers or diesel cylinders). The comparatively small quantities of petrol carried in automobiles is not a grave hazard, though fuel tanks are protected against damage or ignition, and fires do happen. Larger vehicles, on land, sea, and air, often burn the comparatively safer kerosene (aviation) or diesel (heavy machinery). ________________________________ Notes: 1. "Distillate" and "NGL" (natural gas liquids) are used in some instances, and can boil well below 100°C. Butane boils at -0.5°C / 31.5°F. 2. As I'd just mentioned in an earlier comment. I thought a well-known cruise ship or ocean-liner had been converted to petrol, but can't find a reference. <https://news.ycombinator.com/item?id=43344605 https://news.ycombinator.com/item?id=43344605>