ORIGINAL: karolh
The difference that altitude and humidity makes is no stranger to me as I fly from two fields, one at sea level and the other at approx. 3,000', and the carbs require leaning at the lower altitude and richening at the higher one. Needless to say that at sea level the engine makes about 300 more rpm.
Karol
The fact that you gain 300 rpm means other factors than just altitude play a role here. All other things equal, rpm should be the same at sea level or at altitude.