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Elite Member
I did use 87 octane gas in the Stihl for the first year or so and it seemed to run just fine. But the manual says the lower octane fuel may make the engine run hotter, so I do run the 89 octane in all 3 machines now.
I use the lower octane gas in my stihl's, never had an issue. I did "muffler mod" so that heat can release better. I also read in the manual that it said to use high test, but with the mod I don't see it necessary. I run my saws A LOT for fire wood, 35 face cord + a yr{11.7+ full cord}, and lumber milling.