In order to assess the reliability and efficiency of the elevators, a maintenance program is a
significant part of the overall elevator system. Safe and reliable operations are of paramount
importance to the owners and the tenants as well as the visitors who travel throughout these
installations daily [15]. The EU, realizing the necessity of the safe transportation with lifts, issued
directive 95/16/EC of 29 June 1995, on the approximation of the laws of the Member States relating to
lifts. This directive also includes the directive 98/37/EC relating to machinery. Currently, directive
98/37/EC has been replaced by directive 2006/42/EC which also amended the lifts directive [16].
Despite its importance, inspection of the Hydraulic oil quality which was used in the hydraulic
elevators is not a subject of the maintenance program.