I too agree that 4-strokes run cooler.....as I see it in my engines. A 4 stroke would be great in a heli if you could get a bigger cylinder head on it (like 2-strokes) but the valve systems kinda get in the way.... (but a s a side note... I remembering seeing in the Tower catalog a 4-stroke engine for RC Cars.....I wonder how that thing works in that high heat environment?)

As for saying that using 100% synthetic oil in a 4-stroke is bad... I totaly disagree. From first hand experience I find that using 100% synthetic fuel works fantastic...cool engines, smooth idles, and loads of power. Specificaly YS's and Saito prefer the synthetic mix....and the use of any more than 2% Castor in your YS will just give you fuel system problems. As for engine longevity..... I don't believe that using Castor is going to make your engine last longer.... I use and have been using synthetic oil in my fuel for over 5 years and all my engine still run like swiss clocks, and the only parts I've bought are glow plugs...... Making sure you run all the fuel out of the engine after a days flying, using after run oil, and not running lean are much more imprtant to your engines lonfg term health .