How much gas am I saving over 1 km if revs per minute drop from 2400 to 800 while I'm driving?

Yep you can say it's freewheeling ... 800 rpm is the idle speed of an engine so even if you are standing on a traffic light your rpm will be 800... the higher you go in rpm the more fuel your vehicle will consume. I'm not sure how much exactly you will save in cash but you'll definitely be saving money.

I also remember watching a program once, in which they carried out an experiment on a custom circuit to check what kind of driving habit is better when you're running out of fuel to get the farthest. Results showed that if you drive "like a granny" you'll get an extra km or two in a gallon.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.