I run 87 with ethanol,I just make sure I use top quality mix. I try to use only Stihl synthetic. I run it in my 100CC milling saws and all of my firewood saws. I have been building new live edge shelves in my garage for all of my saws. As I'm going through the saws I start them up. My 660 has been sitting for about 6 months and it started right up. My favorite old climbing saw is an Echo 305, about 3 years ago an anti vibe mount broke. When I was building the Echo shelf I found it, pumped the primer bulb, pulled the choke out, and it started right up, on 3 year old gas. I DO NOT RECOMMEND doing that. It's just that I have so many saws, I'll set one down and forget about it, till I get the urge to play with it again. The Stihl synthetic says it has stabilizers in it. I have a Troy Built tiller, Troy Built push mower, and a snow blower that had 87 with out stabilizers left in them and the carbs on all three gummed up. I try to pick one day a month and start all of my gas equipment just to keep it clean, but it's an all day chore, and usually gets skipped.