Will 100 octane hurt the performance if my compression is under 200. I use the Stihl HP oil and the label states to allways use 89 octane.
I am just guessing, don't own a gas station, but in this economy I would think either the cheapest 87 (the bulk of the gallons sold) or the 90+ fuel (guys with much older cars or hotrods) is the most sold at most stations, with 89 falling to the bottom, therefore being the most stale when you get it.
Perfectly happy to be educated on this though, from someone that really knows.
I run 93 no E and echo synblend at 50:1 and it lasts a long time. Not sure how long,. but at least a month. My cutting really varies, sometimes go through two gallons in a day or two, or two gallons over weeks, depends on what else I have to do. I really only cut when I have spare time and no other farm tasks to do. About a month is the longest I'd go with a batch of mix, and it always seems the same to me. Usually I have to get another batch before a month, so can't say really how long it would last and be viable, in a saw with mix I mean, but I had some, just the gas, sit over winter in the tiller and one mower and they fired up fine this spring.
100 octane seems overkill, but if it is all the e-free you can get, what the heck, use it. If it burbles out of the cut and cleans up in the cut, good enough!