This is a write up by PowerMasterFuels. It pretty much mirrors MHO and experience. I pretty much run 15% except for certain engines as a matter of convenience. I get it for only a dollar more than 5% (12.50 /gallon), it's aways immediately available by the case (4 gallons), and I don't have a bunch of different fuels laying around the garage. I run all my engines on 15% including YS 2 and 4 strokes unless the engine shows me it doesn't like it. My Webra 120s almost always indicate they don't like anything over 5%. I could go to the slight pain of ordering 10% or 5% but then my YSs wouldn't like or some of my little .15s might act like I was being a little skimpy. So!!! 15% is the happy medium.

I follow a couple of German forums and what I don't understand is why some of you folks over on that side of the pond skimp on the oil. 12 to 15 percent oil will get more power but at what risk. The oil carrys away a significant amount of heat and is real important for that roll in the smaller high powered engines

The real hygroscopic in your fuel is the alcohol. It is true that nitro is water solueable but getting rid of it won't do anything to prevent water from getting in your fuel. As stated run the engine dry.