I would vote for Stihl also. I like to purchase 100% gasoline...not anything with an ounce of ethanol in it. Others have good luck with Stabil or like additives. As posters above point out...drain the gas if used infrequently. I drain gas tanks on 2 stoke devices I can easily flip over...large 4 strokes like mowers or tillers I put a cut off valve in the gas line and run them until they die from lack of fuel. Purists may point out starving an engine struggling to run is lean/harmful...no problems so far. All start on first pull with the addition of fresh fuel next time used.