Mobil Stern Tube Lubricant is a high performance, high viscosity lubricant developed especially for the lubrication of Cedervall-type stern tube bearings used in ships and for certain bearings of ships’ fin stabilizers. Mobil Stern Tube Lubricant is formulated from relatively high Viscosity Index (VI) base oils combined with emulsifiers, structure modifiers, surface active agents and corrosion preventives. It emulsifies readily with seawater to form a stable water-in-oil emulsion that is adhesive and an excellent lubricant. It provides effective rust protection in the presence of seawater and the lubricating film is resistant to water washing so that corrosion protection is maintained for extended periods under severe operating conditions.Where the propeller shaft passes through the hull of a ship, it is supported by a bearing that is housed in the stern tube. Three distinct types of bearings are employed in this application: 1) The lignum vitae bearing, which has a stuffing box on the inboard side and no seal on the outboard side, is lubricated by seawater. The stuffing box may be lubricated with grease or oil, if this is deemed necessary. 2) Bronze or white metal bearings having oil-tight rubber seals on the inboard and outboard ends normally are filled with a lubricating oil that readily separates from water. Turbine oils, engine oils or hydraulic oils of the required viscosity generally are recommended. 3) The Cedervall type, which is a bronze or white metal bearing having an oil-tight inboard seal or stuffing box and metallic outboard seal that is not fully oil-tight, requires a lubricant that readily emulsifies with water. Mobil Stern Tube Lubricant has been formulated to meet this need. With the Cedervall type bearing a high viscosity lubricant generally is supplied to the bearing from a gravity tank located above the waterline so that the lubricant is under sufficient pressure to help exclude water from the bearing.