Abstract: The operation of marine diesel engines is improved through use of a defined fuel composition, containing one or more additives comprising a methal detergent, a non-metal detergent or both. The fuel is supplied to Diesel engines which operate in a maximum speed range of 1000 rpm (4-stroke engine) respectively 2500 rpm (2-stroke engine). The power output is greater than 200 bph. The cylinder bore is greater than 100 mm (2-stroke engine) while the piston stroke shall be greater than 150 mm (4-stroke engine) respectively greater than 120 mm (2-stroke engine). The metal containing detergent is a neutral calcium sulfonate, salicylate or calcium phenate. The non-metal containing detergent is a hydrocarbyl succinimide.

Abstract: Engine operation is improved by means of detergent additives. An additive comprising, or obtainable by admixing, A or B or both wherein: A is a metal-containing detergent, and B is a non metal-containing detergent, is used in an internal combustion engine lubricated by means of a separate lubricating oil system, to enhance the properties of the lubricating oil of the engine through entrainment therein the combustion chamber during operation of the engine.