Yeah, crusing below 4000 rpm is very economical becuase the torque sweet spot is inside the range so the weight of the car does not really matter.
I am one of the least "brake happy" drivers around. I brake very late and very hard, so that helps in the FC. I did 320kms in an elapsed duration of 9 hours and it consumes 30 litres.
If I were in Msia, I could do Singapore to KL and back twice and it would not take 9 hours!.