Guys, I'd like to go back to normal 20w 50 oil fromt he Yamaha Semi Synthetic I've been using for about a year and a half. My dealer says I should not go back once I've gone synthetic. Is he BSing me to get the $7 a bottle or will there be no side effects what so ever? I'm going to go with the Valvoline Motorcycle Oil now available at Wal-Mart for cheap. Anyone gone from Syn back to normal?