Alcohol is hygroscopic, meaning it will draw moisture out of the atmosphere. It's contaminants like water that make fuel go "off." Some will argue that petrol can go bad in a matter of weeks. Personally, I view fuel older than six months as suspect.... Stabilizer and a properly-sealed container can help, but there's still alcohol in the fuel Why alcohol is there in the first place is debatable, especially as it 'costs' more in energy to create than it produces - the only thing it really does is enrich a few very large corporations - but I digress.

I have a 35 year old Stihl chainsaw that started running poorly a while back, so much so that I bought another as a replacement. A friend who has a real skill with Stihls rebuilt it and got it running a sweetly as new - better than the "new" saw.

Stihl recommends their brand of fuel without alcohol, packaged and pre-mixed in one litre cans. They claim the sealed can has a near-infinite shelf life if unopened and pretty lengthy even after opening. Others make similar canned fuel.

It all depends upon your usage. If cutting a lot, then your fuel won't be sitting around long enough to go stale. If you need a saw only occasionally, it might make more sense to buy the canned stuff. In any event, you don't want fuel sitting in the saw, mower or generator for any significant length of time - like the five gallons sitting in the generator from the last hurricane season. (I installed a fuel drain line on my 8,000 watt generator.) Drain, start and let run until it stalls.

"Regular gas (with ethanol) doesn't burn hot enough..." Bull crap. does that place have a real clue about engines? Nice excuse to avoid work. Higher octane is harder to burn as in higher compression in cars like the Corvette. Obviously, your trimmer is a weee bit below a corvette but Stihl's manual does say to use it because it burns cooler. (personally i use regular on my 70's stihl fs80s)

Get a can of the starter spray- for some here, dont get your panties in a wad its not going to kill the motor and hey, its a poulan. spray some and try then- no choke needed. if no put put, disconnect the kill switch and try again. Myself 99% of trimmers\blowers i find at the curb have a fuel delivery problem usually loose fuel hose from shrinkage.

...and the fuel and/or carb gasketing on some of the older units doesn't like alcohol at all. Fuel tubing, too....

My friend with the mad Stihl skills has made quite a few coin 'flipping' saws. Buys non-running units for next to nothing but gets 'em running again cheaply.

FS80...damn good brush cutter.... As an Appalachian Trail overseer, the Stihl factory gave me one for trail use. Used it four or five times a year for nigh on 20 years, but each time for 8+ hours, pausing only long enough to refuel or swap blades. My section of the AT was where "the incident" from Bill Bryson's "A Walk in the Woods" took place. In the book, the two critters were never identified (bobcats, most likely) but in the movie, they were grizzlies! There haven't been grizzlies in Virginia since the last ice age....

The Stihl developed fueling problems I couldn't resolve, so I gave it to my friend mentioned above - another trail overseer - and the Stihl lives on to this day.