Combines Understanding Rotor loss

Yep, your right. Everyone gets to pick where the needle reads. However, when you are consistently running in one spot (my Dad likes to run with the knob set at 4.5) then you get to know how much is going out the back as the field conditions change. In speed mode you can do the same thing, but you just have to make sure that you are traveling a reasonable, constant speed to keep from dividing by a small or changing number.

Yes, but when it divides by speed, it gives you a loss_area, which is what you are after anyway. If you want the absolute loss out of the back of the combine to be the same at all speeds, then your least loss on the field will come when you drive the fastest. loss rate per time is very deceptive because at slower speeds, the loss rate is lower per time, but may be higher per acre because you are driving slower.