The objective is to give recommendation of lubricants f�r "environmentally acceptable lubrication" systems such as thrusters with respect to chemical contents and their tribological properties. Glycerol-water based fluids as candidates for next generation "natural lubricants" are evaluated. Improvement I lubricant maintenance with combination to condition monitoring. 1. Lubricant candidates as mineral oil alternatives: Specific additive for synthetic esters have not been well studied so far. Candidates of lubricants will be discussed in the light of operation conditions of thrusters, structure of oil and additives, and their contents in formulation. Particular emphasis will be put on chemical structure of anti-wear and extreme pressure additives for fatigue mode.