How long did merchant shipping continue to use coal after navies moved toward oil?
Short answerPossibly into the late twentieth century, because some coal-fired ships were reportedly still being built in the 1960s and remained viable where coal supply and mechanized handling favored them.
NotesThe last newly built coal-fired merchant ship may date from the 1960s, although that recollection is explicitly unverified. A ship of that generation could then remain in service for roughly another quarter-century. Coal still made economic sense in regions where it was readily available and oil supply was less convenient. Mechanical shovels and conveyors also removed some of the labour penalty associated with hand-fired machinery. The energy transition was uneven across routes and commercial conditions rather than a single fleet-wide conversion date.