The cation mobility μ+was measured in n-pentane at 295 K and inn-C6to C11andn-C14alkanes from ~295 K to their normal boiling points. The dependence on viscositywas reexamined and the best fit occurred withp = 1.0. The ratio of diffusion coefficients of neutral molecules to analogous cations was ~3 because of the stronger interaction of ions with the fluid molecules (electrostriction). The dependence of μ+on free volume is illustrated.Keywords: thermal cation mobility,n-alkane solvents, viscosity effects