Aging of motor oil is characterized by diverse NMR methods to get insight into the chemical processes' which occur during aging. Already one-dimensiorial H-1 and C-13 spectra reveal the relevance of chemical aging also with respect to the mechanical behavior of oils. As NMR is a quantitative analytical method, the absolute chemical changes can be observed:and quantified. In addition; the spectral interpretation in terms of chemical composition is confirmed and deepened by two-dimensional H-1-H-1, H-1-C-13, and H-1-N-15 correlation spectra, as well as,diffusion and relaxation experiments. The different NMR results are discussed and interpreted to obtain a thorough picture about aging processes of motor oils.