Here in the US the winter blend in cold climates is completely different ( I'm in New England). If you use winter fuel in the summer it can boil on you in the hot weather near hot engines and cause run ability issues. I just went through this ( separate from my surge issue I posted on a couple months back). This was more rough running and some backfire issues after the engine warmed up in this hot weather. I had been seeing bubbles in the fuel filter about half way through mowing my grass. I was running off winter generator gasoline I had stored. Today I got fresh gas , the problem is gone. All of the problem is gone, the engine runs smooth and no bubbles. The old gas was fine, not that old, had stable in it etc, just the wrong formula.
This isn't my idea, I got the thought off a motorcycle forum while actually looking up octane issues for old Goldwing motorcycles.
