Marine lubricants are scientifically designed to meet the specific lubrication requirements of every type and size of propulsion machinery and protect the engines and shipboard equipment. These lubrications include the use of ancillary grades such as hydraulic oils, compressor oils, gear oils and grease. These lubricants when used as propulsion units, marine diesel engines are coupled to the propeller shaft through a gearbox because of their speed. In trunk piston engines, a single lubricant is used for crankcase and cylinder lubrication. All major moving parts of the engine, i.e. main and big end bearings, camshaft and valve gear, are lubricated by a pumped circulation system.