what fuel do you guys recommend! i have been using traxxas top fuel 20%. its about 28 bucks at my local hobby store. i was wondering if there is any other good brand out there that might be a little cheaper. also i always wondered why traxxas made different percentage fuel grade. why is that? and why is it that i can't go to 33% if i broke in with 20%? how long with the fuel will be good for if not using for a long period of time? thanks