Hi!
Your friend must have missunderstod it!
What nitro does is enhance your ability to set the engine correctly. It broadens the fuelneedle setting and makes the engine run cooler if set correctly.
By using nitro You can get a more perfect engine setting which makes the engine run cooler, reducing wear and tear.
Personaly I use 5% nitro in my fuel, I mix it myself , consisting of 15% Motul "Micro" a French all syntetic oil , 5% Nitromethan and 80% Methanol.
Most flyers over here in Sweden do use nitro, 5-10% seems to be the norm.