JulesMaximus
No Lifer
Well, most people are worried about tires cracking/drying out, which makes sense because they're the rubber component exposed to the most sun (generally). I think that anything that will protect the rubber from UV, ozone, and oils would work just fine. Armorall is a silicone rubber/plastic dressing, and I imagine so are things like tire black, et al. I bet any of them would help.
The fuel argument is that 93 octane has less crap in it than 87, which has a larger amount of crap that will break down faster or evaporate faster as compared to 93. 93 will also have more detergent additives, which will probably help keep your fuel system a little cleaner. Is there a big difference? Enh, debatable. Is the cost difference enough to really care? Definitely not. For $1-2 more it's worth the peace of mind IMO.
D: No, definitely don't put anything on your tires!