I want to get back to the topic at hand, forgive me.
I also wonder how best to dig, save fuel, time, wear, while moving the most dirt possible.
I watched letsdig18 on youtube, he seems to have it figured out.
A couple things he doesn't do, that i find myself doing often. He doesn't plunge the bucket into the material. Rather he lets the teeth do the work, filling the bucket as he proceeds through the pile. He uses the entire crowd distance to fill the bucket, and used the crowd to fill the bucket. This is opposed to plunging the bucket and filling by curling.
Also, using the teeth to do the work ensures system pressures are kept low. He never stalls, or comes close to stalling the hydraulic system. You can really be gentle, yet fast, by focusing on avoiding high system pressure...ie. forcing the engine to work to create massive pressures.
I think an analogy is in order here. Imagine a pull pan scraper. I've never seen one myself, but its easy to imagine how they work. You travel a long way with the blade barely in the earth, and it fills itself nice and easy. But if you plunge it into the earth too deep, you stall the tractor, resulting in wasted energy, higher wear, lost time and so on.
Lastly, another thing he does i simple cannot do, is he leaves the bucket curled out after dumping. The lesson here is focusing on directing the oil to the circuit you want to use. Personally, i am running all the circuits all the time. Returning to the pile i tend to boom up, crowd, curl in, and swing simultaneously. But when i get to the pile, i have to undo it all by curling out, booming down and extending, wasting precious time. So my focus tends to be on oil flow, and where i want to use it. I get more done by thinking about what my hands are doing, and what i am telling the machine to do. I think that problem is specific to me. But i do get more done by really focusing on not wasting oil flow on unnecessary motion.
Anyway, that's my two cents, and i have a long way to go before fast and efficient is natural for me.
ps: I have always thought a really neat training tool would be a pressure gauge in the cab showing peak working pressures. It would give a perfect indication of what you are doing to the machine.