I've seen bunker fuel in a ship, and its consistency was best described as "tar-like". Mind, n=1 and uses may vary, but bunker fuel can be exceedingly thick.

I've seen bunker fuel in a ship, and its consistency was best described as "tar-like". Mind, n=1 and uses may vary, but bunker fuel can be exceedingly thick. All the more so on high-latitude routes with fuel tanks near the outer hull and cooled by ambient water temperatures near freezing. Decidedly thicker than automotive oil, and probably thicker than axle grease or vaseline / petroleum jelly. The ship in which that was used (triple-expansion steam engine, late 1800s design, built and used during WWII) directed spent steam around the incoming fuel flow directly prior to boiler injection, and that steam then wrapped around the fuel line and part of the fuel tank itself to heat the oil to the point it would flow. Side note: Venezuelan oil is very thick and viscous, and requires mixing with lighter fractions of petroleum to be pumped out of wells. Venezuela typically imports what would otherwise be waste light fractions of petroleum, generally from the US or Nigeria (heavily dependent on political winds) in order to do this. A significant fraction of US petroleum exports go to this or similar uses. (I suspect Canadian tar sands see similar treatment though I don't have a source on this.)