A fuel additive for use in the treatment of diesel fuels to reduce polluting emissions during the combustion of such fuels wherein the additive composition is formulated to contain mineral seal oil, mineral spirits, a glycol alkyl ether and at least one alkyl aromatic ethoxylated surfactant. The invention utilizes passive air rotation techniques in combination with centrifugal separation and a particulate reservoir to achieve highly efficient, highly effective separation of, e. The respective roller body tracks of the bearing outer ring are aligned with the respective roller body tracks of the bearing inner ring and a row of roller bodies is disposed between each of the respective sets of roller body tracks. The rail is fixed to the boat between the steering kite and the steering device in such a way that the traction force of the steering kite produces torque about the longitudinal axis andor the transverse axis of the boat in the water, by means of which the leeward side of the boat is lifted upwards. Reservables are searched out in the database for matching with received customer requests in the process of forming the service engagements identifying reservables, which are no longer available in whole or in portion thereof.