The crankcase will have a life-time fill of 30 wt., maybe about 30 tons in a dry sump. The combustion space is sealed from the crankcase so products of combustion do not get into the crankcase. This oil is continually centifuged.
60 wt. or 70 wt. TBN 70 oil is injected into the walls of the cylinders to lube the pistons skirts and the liners. This oil is burned or collected in a waste oil tank. The big engines will consume about a ton of this oil daily. The high TBN is needed because of the 3% sulfur in the very heavy fuel oil. Diesel fuel similar but dirtier than #2 is only used when the engine will be allowed to cool down for repairs or layup periods. Otherwise, the heavy oil at about 250°F is continuously circulated through the piping and injectors at all times. The engine is started on heavy fuel.
The engine is directly connected to the propeller. The engine is run in reverse to run the propeller astern.
These engines are licensed from Warsilla of Finland, MAN-B&W of Germany, or Mitsubishi of Japan. They are all made in Asia, and any of the engine makers can make just about any of the engines. The biggest I've heard of is a straight 14, 7400 hp per cylinder, almost 104,000 hp total. They are all straight two-strokes. The last one I ran was the biggest of its day, a Sulzer 12RTA84, 12 cylinders, 84 cm bore, 57,500 hp @ 95 rpm. Four 6' diameter turbochargers.
Ken