7 1/2 or 8's...
92,93,94 octane is a must. If you can find without ethanol then great, if not then use a chemical treatment. Straight Stabil does not treat ethanol.
I have ran multiple small engines out of fuel using stabil, specifically my Sthil weed eater that I bought in 1998. It smokes and chokes and then dies and finally starts each spring.
A fellow that is very knowledgeable and has started a very successful small engine business (about 15 years now) told me about two years ago that now with the ethanol and other crap being added, stabil is no longer good enough. This guy claims that he runs STAR TRON enzyme treatment in his own stuff.
I have been using that for a couple seasons now and I guess it works? As all of my stuff still starts up easily in the spring.
We are talking about the following:
1) 500CC ATV - purchased in 1999 or so.
2) 23HP Briggs on lawn mower/tractor, 3 years old with about 200 hours on it.
3) Echho leaf blower- 2011 purchase
4) Sthil weed eater- 1998 purchase, just replaced carb this spring after 14 plus years of use for $30 bucks.
5) Honda generator purchased in 2005, fuel drained every six months and replaced with fresh fuel (plus stabil and star tron added) even when not used, started every six months and ran for 30 minutes.
6) POS Craftsman / briggs power washer that I wish would die but won't because of the way I take care of equipment. I am not pleased with the pump and the way it fails to adequately dispense from the solution containers. The engine runs fine...
7) Troy Built snow thrower with snow king engine bought fall of 2005, runs great.
8) Huskavarna 455 rancher chain saw purchased in 2006 or so.
So bottom line, I am all in with this STAR TRON stuff or the stabil MARINE as it is suppose to combat the harmful effects of ethanol.
As far as running something dry vs. keeping full with all the chemicals, I guess the big factor depends on how long you are going to not use that blower. A couple months and you are good empty or full with chemicals, IMO. If you are going for long term storage say 6 months or longer, I would treat fuel and keep completely full and then swap out treated fuel for six months if still not going to use.