The 10* for 1 hp thing may or may not be that accurate. Think about the power the SC has on a 50* morning and then what it lacks on an 80* day. That is a 30* difference in temp. Compressing air (assuming no pulley change) will be at a constant rate for a set rpm. Therefore the temperature change will also be constant once the air is compressed. I don't know about you, but 3hp I won't feel, but I definately feel more power on a cool morning than I do a warm to hot day. So I have to think that temperature fluxuations affect hp much more than 10* for 1 hp. But that's just me thinking too.