Most diesel engines that power ships like supertankers are built so that the engine can safely use low-grade fuels due to their separate cylinder and crankcase lubrication.
At only 300 feet long, many ship captains of these giant supertankers worried that they would run aground, but one did come in and found the water is deep.
The use of such large ships is in fact very unprofitable, due to the inability to operate them at full cargo capacity; hence, the production of supertankers has currently ceased.