I used to use nothing but premium. I didn't get a batch of bad gas, but I got some additive-ladden gas in late spring, early-summer that made my bike detonate like a mofo. My dealer said that the additives used to reduce emissions in winter can really lean out the bike in warmer weather, and since premium doesn't sell as fast as regular, there is still plenty of the additives in the premium, sometimes well into the summer. Then he said run it on regular for a little while - it won't hurt the bike.
