The possibility to diagnose quality of motor oil by using the method of surface plasmon resonance (SPR) for comparison of optical refraction indexes inherent to the initial fresh oil and to that used for different exploitation terms. This comparison enabled authors to determine not only the motor oil degradation level but also availability of wear particles from motor parts. Investigated in this work were four samples of the motor oil Genuine 5w-30 dexos 2, namely: the fresh one and three ones taken after car mileages 180, 430 and 712 km. When measuring the kinetics of refraction indexes for the studied samples of used oil, the authors observed a characteristic “shoulder” caused by sedimentation of oxidation and wear particles on the surface of SPR device sensitive element, while in the case of fresh oil there took place only the temperature drift of the refraction index. It has been experimentally shown that using the SPR method improves more than one order (from Δfmin = 0.17 vol.% down to Δfmin = 0.0107 vol.%) the detection limit and enhances sensitivity of measuring the wear particles concentration in motor oil as compared with the known refractometric method. Application of the optimum concentration (50%) for the solution of this oil in rafinate of benzene reforming provides the 3-fold increase in the sensitivity and selectivity. Thus, it is experimentally proved that the SPR method can be offered to control quality of motor oils as well as the degree of wear inherent to interacting parts of machinery.