Drafting, as u put it, is a very useful technique.
Often on the motorway from Hyderabad to Karachi, the wind is very strong, so strong in fact that u can go down a steep incline and still decelerate!
No matter what u do, there's always going to be this one dude in a Corolla or Civic who'll push his car to keep up the speed.
If I cant find someone of this sort, i am happy with doing 80km/h. Excruciatingly slow, but hey, there's little load on the engine.
If i find someone like the above mentioned, i oblige by sticking to their rear bumper and enjoying their car's aerodynamics
Coasting is something my dad taught me to do when I am out of fuel, but i practice it more often cuz its actually fun. The car goes all quiet, silent and peaceful
and ur saving fuel.
Its like that childhood act, asking someone else to push ur swing and enjoying swinging without effort
and turning the car off IS NOT RECOMMENDED since most cars these days lock up brakes and the power steering and other electronics turn off. Highly unsafe at highway speeds of around 100km/h.