In this paper the study is directed to a condition-based predictive maintenance concept as an alternative policy to determine a fleet's health, for increasing the fleet availability and to reduce the operating cost. The concept is based on predicting the system degradation by using an expert system. Therefore, the decision-maker can calculate the remaining lifetime for any mechanical system. These calculations help the decision-maker in making a repair or replacement decision in a suitable time. An application is presented herein on the cylinder kit components (piston, piston rings and liner) to illustrate the effectiveness of this technique. The results indicate that knowing the wear between the cylinder kit components in automotive engines is very important to plan the maintenance for making the repair or replacement decision in a suitable time.