Bottom line:
Yes - you can change fuel
Yes - you can change brand of fuel
Yes - You can change nitro % content in fuel
YES YES YES!
I would never suggest running over 30% and never running anything under 10%
I prefer to run 20% all day long and have done so for 2 years now with no problems in ANY of the mills I run it in. From break-in process to break-down process, I have always run Odonnle 20%.
As Sky stated - you will want to run a tank through just to get the mill aquanted with the new fuel. More-so, you may need to adjust your needle, up/down a hair to compensate for the change in nitro %.
I suggest adjusting in this order:
Idle
Low Speed Needle
High Speed needle
Then back to idle again
Done.
I can't stand when LHS's say you can't change fuels etc. It just pisses me off.