Marine lubricants are oil formations that are used in various types of machinery located on large ships. Due to the shear size of the ships as well as the high amount of fuel burned, there are many difficulties presented with developing a truly marine-grade lubricant.Typically, there are three main ways marine lubricants are used: with propulsion engines, auxiliary engines and power generation, all of which require the use of one of two types of engines: crosshead and trunk piston. Crosshead engines are large reciprocating diesel engines that can be either internal combustion or steam, but are modernly more likely to be internal combustion. Crosshead engines are typically two-cycle and operate at slower speeds than trunk piston engines. Trunk piston engines are internal combustion diesel engines that operate on distillate fuels and are typically four-cycle and offer medium speeds. Unlike crosshead engines, which have a separate cylinder and crankcase sump, trunk piston engines have a common sump for both parts. Additionally, marine lubricants can be used in variable pitch propellers, geared transmissions, turbochargers, deck machinery and oil-lubricated stern tubes. A fairly new technology that is increasing in momentum is biodegradable marine lubricants, which a few companies have developed in response to increasing demand because of the environmental benefits these lubricants can offer.