The rotational tunneling states of methyl groups are subject to severe symmetry restrictions which result, at sufficiently low temperatures, in extremely long lifetimes. Hence, these states can be used to store population and to do hole burning experiments. From the recovery of the holes the relaxation of the rotational tunneling levels can be measured. We performed experiments of this type with the probe molecule dimethyl-s-tetrazine in a series of n-alkane host materials. The methyl group turns out to be an extreme sensitive probe for the host lattice. Direct-, Raman- and Orbach-type rotational tunneling processes could be identified, with surprising details for the d-substituted rotor.