Products of thermal dehydrogenation of C60H18 (which mainly occurs at 450-600 degrees C) were studied by XRD, Raman, IR and mass spectrometry. IR spectra indicate that dehydrogenation resulted in partial recovery of pristine C-60. XRD data indicate that the cell parameter of the face-centered cubic structure, which is higher for C60H18 (14.55 angstrom) than for C-60 (14.17 angstrom), remained higher following heat treatment, and heating at >500 degrees C caused further expansion (to 14.78 angstrom). The increase in the cell parameter correlates with the beginning of partial fullerene cage collapse (corroborated by IR, Raman and MS data) and is suggested to result from "self-doping".