I noticed that toward the end of last year's riding season my fuel economy took a dive. My mileage dropped to around 33 M.P.G. When putting away the bike for the winter I checked my spark plugs and noticed they were black. It was late October and early November when I noticed this change. I am wondering if that is when the fuel producers switched over to their winter blend. This drop off in fuel economy was more pronounced last year than in years past. Did anyone else notice such a radical drop in fuel economy with no other possible causes than fuel quality?