The only engines i've stayed away from Nitro are Moki's and Lasers. Everythig else has 15%, both 2 and 4 stroke except the YS's that drink the bank bustin' 30%. I experimented some years ago with an OS 1.20 Surpass on 0-5-10-15-20 and 30%. No questions, nitro helps all round running, tunning, response... the list just goes on. Engines just benefit, they're just happier! And if the engine happy, so is the pilot. Having said that... 5%-10% what's the point? You're getting some benefit, but not max benefit. 15% was absolutely the optimal place for me for sports engines. The most cost effective, max response deal. But the two strokes on 15% do seriously benefit from one extra head shim. Drop down to 10% and the shim isn't necessary but you loose out on response and stability. 15% and Enya 3 or F plug (specially in inverted 2 strokes) plus 15%... Shorts out 98% of all troubled engines.For some reason, people believe that nitro is all about adding extra power. Nothing could be further from the thruth IMO. The engine can only deliver what it's designed to deliver... and it'll never realize that unless you run it the way the manufacturers do. That means 15%.