ORIGINAL: Fs one
Why pay more money for 15% when it will make no more difference in performance.You need 15% if you are using 4 stroke engines
You are leaving out one very important reason to use higher nitro in two strokes as well as four strokes and that reason is in fact density altitude.
Flatlanders who seldom fly anywhere else have a hard time with this concept but if you fly at the higher elevations the fact is higher nitro contents can and will make all the differance in the world and it not only makes a differance in the power of any two stroke/four stroke engine it even can make the differance in the ability to fly at all at the higher density altitudes.
Thirty miles away the fields down there at 500 feet elevation, the fellows all do just fine with 10% fuel and some even o% However three thousand feet higher at my field to get the same engine performance it takes 15%.
Now just hundred miles to the east of here at a field almost 7000 feet and density altitudes reaching over 8000 in the summer you are not going to even get off the ground with your flatlander fuel in many cases. When they have their annual fly in they recomend to the flatlanders to bring 25% for two strokes and 30% for four strokes.
Or for some who just have to use their 10% up there, everyone always gathers for the fellows takeoff
So indeed there is a viable reason for many and it certainly does make a differance.
John