Mobil Stern Tube Lubricant

Mobil Stern Tube

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. 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.

Advantages and Potential Benefits:

The requirements for lubrication of these three sets of bearings in the stabilizers and stern tubes are sufficiently similar so that a single, carefully formulated lubricant can be used for all of them. To perform satisfactorily, however, the lubricant must have the correct viscosity to flow properly under gravity head without excessive rapid flow that would result in high consumption; must minimize wear under the heavy loads encountered in the bearings; must protect the bearings and other components from corrosion and must emulsify with any seawater that passes the seals in order to maintain lubricating characteristics and minimize corrosion.

In stern tube applications, consumption of the lubricant is a major concern, both from the standpoint of the cost of the lubricant and the cost of labor required to fill the tanks. In two ship trials conducted over an extended period, Mobil Stern tube Lubricant gave significantly reduced consumption compared to the previous formulation, and at least as low as the best competitive product. Throughout the tests, lubrication was entirely satisfactory. These results indicate that Mobil Stern Tube Lubricant provides effective and low cost lubrication of stern tube bearings.

  1. Selected viscometrics means effective lubrication of critical stabilizer and stern tube components
  2. Good emulsification properties means that the lubricant emulsifies readily to maintain lubrication in the presence of seawater
  3. Excellent rust and corrosion properties helps protects critical bearing surfaces exposed to seawater
  4. Multi-use capability reduces the number of lubricants required on-board
  5. Good viscosity retention in severe applications aids in effective leakage control and reduced oil consumption


  1. Mobil Stern Tube Lubricant is recommended for the lubrication of Cedervall-type stern tube bearings on ships where a high viscosity, readily-emulsifying lubricant is recommended by the manufacturer.
  2. It is also recommended for the lubrication of fin tilting bearings, as well as the crux trunnion bearings of Denny-Brown-AEG ship stabilizers and is approved by the manufacturer for use in these applications.



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