With low fuel prices, I decided to splurge on premium gasoline, thinking I might get better mileage and performance. Soon after, the check engine light began to come on in stop and go city traffic, and the idle would stay quite high. I'm thinking unburned fuel is triggering the emissions sensor. I put a tank of premium once on a long road trip with highway driving and didn't have this issue. I'm thinking the stop and go aspect is causing issues with the premium fule. Once I run through this tank, I'll fill it again with regular fuel. 87 octane is recommended in the owner's manual. I suspect there is a good reason for that. Has anyone else had issues with premium fuel? My bike is a 2015 Street 750 that I purchased in May, 2015 and have ridden daily since.