We present results of nonlocal and three-terminal (3T) spin precession measurements on spin injection devices fabricated on epitaxial graphene on SiC. The measurements were performed before and after an annealing step at 150 degrees C for 15 minutes in vacuum. The values of spin relaxation length L-s and spin relaxation time tau(s) obtained after annealing are reduced by a factor 2 and 4, respectively, compared to those before annealing. An apparent discrepancy between spin diffusion constant D-s and charge diffusion constant D-c can be resolved by investigating the temperature dependence of the g factor, which is consistent with a model for paramagnetic magnetic moments. DOI: 10.1103/PhysRevB.87.081405