___Fuel additives are bunk. Fuel … Most come from the same place anyway but a newer station usually has less chance of contaminants in the storage tanks then an older one. I use both Shell and BP just because I have their CC’s and they actually save me a few cents vs. the no names. I used to fill up wherever and never really saw a difference in FE so just consider the CC deals as the ace in the hole.
___Tires, start at 44 #’s all around if you are high already … You can work your way up from there. If you are currently running 32 as an example, why not do a 35 all around for day 1 and 2, 38 for day 3 and 4, 42 day 5 and 6, and 44 day 7 forward.
___Tire pressure is the easy item. The fuel stuff is bunk no matter what professional mechanic you have spoken with telling you otherwise. If they insist, ask them when was the last time they doubled the EPA combined not using the concoctions and that will hopefully silence the experts that have not been there/done that … You next oil change … Well, you know what to do about that as I am sure you read the right articles floating around here for that
A clean air filter is something I will recommend however. Not a K&N or CAI (Cold Air Intake) but a simple air filter change can at least remove some pumping losses vs. a dirty one. Your FE will come from the techniques you will soon be accustomed too, the setup just gets you into the ball game in my experience.