General requirements of cylinder oil
1 It must have required level of Alkalinity (BN ).
Base number is indicative of strength of Alkalinity usually KOH or Caco3.
70 BN Means 70 mg of alkali in 1 gram of oil.The alkali level depends on the sulphur content of residual fuel used.If too less,will cause corrosion in the form of “clover leafing ” and if excess ,it will results in calcium,salts deposits on piston crown and top lands to cause further abrasive wear.
2.It must withstand temperature , variation and resist oxidize degradation.
3.It must be of higher viscosity (SAE-50 ) to form a good lubricating film between liner and ring and hell to prevent blow past.
4.Typical values of sulphur content of 0.5 -1 % may have BN if 5 -15 and those above 1.5 % have 40 or higher.
