NMR relaxometry analysis of lubricant oils degradation

The present work was undertaken in order to investigate lubricant oil degradation at the molecular level. Ageing effects, as reflected on the proton spin-lattice relaxation rate (T −1 1 ) dispersion, were studied in two different lubricant engine oils. The proton field cycling technique was used to scan relaxation of new and aged samples of monograde and multigrade oils. Relaxation dispersions were interpreted in terms of self-diffusion and molecular rotations. Our study shows that proton T −1 1 could be very sensitive to degradation processes, especially at low Larmor frequencies. The analysis reveals a noticeable sensitivity of the involved correlation times. The pros and cons of the technique are also discussed.