Abstract: The relevance of the wear type diagnose of various parts of model 8NVD48A 2u diesel engines is established by summarizing over 600 practices on wear failure diagnose of the diesel engines, based on the field oil monitoring results and various other testing experiences. The combined reliability of the wear failure diagnose to various parts of diesel engines is given based on Dampster Shafer theory (briefed as D S theory). Five combined wear failure modes of the parts have been found from the wear failure modes including the scoring, seizure, and corrosion of piston and piston ring/cylinder liner pair, the scratching, seizure, spalling, and corrosion of gears, and the pitting, seizure, and fatigue of gears, by using genetic algorithm. The applicability of various oil monitoring methods to the diagnose of the five combined wear failure modes has been established. Thus a new train of thought is suggested for the diagnose of the combined wear failure modes by introducing genetic algorithm into information fusion method.