Question about throttling and stuff when driving

by Kemrich
(Washington)

So I have a friend, now I know this is weird but we have had this debate for too long and I need answers, and he plays ETS2 (Euro Truck Simulator 2) and ATS (american Truck Sim) and when he drives he babies his throttle, just to get a better mpg.

He never pushes the throttle more then 50% (very rare) and it doesn't matter what his weight it, is this a normal thing to do with semi's is it even healthy for the truck and engine?