I was told that a chainsaw has two speeds, idle and wide open when cutting (under load). This info is on the Husqvarna website and the claim is that the engines are designed to run at full throttle under load, matching the engines ideal torque curve. The implication is that this is the ideal condition and reduces stresses on the engine. Having said that I have a Stihl MS660 and an Echo 16" for small stuff and both run full out. I use the Stihl with a rip chain for milling lumber and it runs wide open for hours with no problem. I like the Husqvarna site because they have a lot of advice on it and I really don't think there is much difference in small engine operation between brands.