In fact, let me one thing clear.
Oxidation is NOT loss of electrons, if it were, ionic compounds would be formed. Oxidation is the giving away? of electrons such that the oxidised species gives up it's electron for most but not all the time. Therefore, considering ionisation energies in redox reactions is absurd as no ionisation takes place in most redox reactions (sometimes they do, as with transition metals). What you should consider is that, will the species that gives up it's electrons be more stable? and will the species that takes the electrons be stable? will the overall compound be stable?
Again, the process of oxidation is always met with reduction as it's, again, not losing electrons, but unequally sharing electrons. Oxidation of hydrocarbons is exothermic for reasons I stated above. Sometimes, a compound would be less stable if it unequally shared it's electron, like the oxidation of copper (0) to copper (1).