Sure you can change fuels!! How are you gonna know what runs the best in your engines? You have to experiment. Just don't mix fuels.
Mind you, you must (I know some are gonna disagree) break in your motor/retune for a couple of tanks with the new fuel. After that, set your needles and go for it.
pinky2252s, the main reason people work at hobby shops is to make money. They were trying to hustle you. You know that!