Lubrication is critical to the life of a gear coupling, so the lubricant should be selected carefully. At minimum, the grease should be a quality coupling grease (NLGI Grade#1) which meets the minimum requirements shown in the Kopflex installation instructions. Because of our confidence in Kopflex greases, a 3 year warranty is offered when Kop-Flex KSG or KHP grease is used in Kopflex couplings. In addition, FAST'S couplings may use oil (SAE 140 Gear Oil is recommended). Do not use bearing greases or greases containing molybdenum disulfide (moly) in standard gear couplings. Consult Kopflex Engineering for special applications: very high speeds, very low speeds, high temperatures, etc. Universal joints can use a grade 2 bearing grease. Standard gear couplings should use Kopflex KSG coupling grease. For gear spindles, Kopfllex Waverly Torque Lube ""A"" or Syntech grease is available. Please see link for additional reference.