...maybe i can add some inside thoughts from PAG - YES, you´re right Porsche is taking the whole economy thing quite serious - i think we can say, although no one really speaks about that - that Porsches always had a very good fuel milage for sports cars and the F6 is kinda penuriously with the expensive Super Plus fuel...
one can easily drive a modern 911 with something around 10ltr - but especially here in germany this is kinda hard to reach...
...personally i ride the 955 with everything between 14 and 20 ltr with lot´s of autobahn parts but i have to admitt that i´m not very keen on a good fuel milage - just want to cross my distances as safe and fast as possible...
in general we can say that the more u depress the accelerator the more fuel consumption u have, regardeless at which speed u´re driving, this is all controlled by the ECU and present accl. pedal position...
so i´d say when u want to safe some fuel be gentle on the accl and do not revv to high - with a gasoline engine u can upshift at 2000rpm on a diesel at 1500rpm - of course depending on the power of the engine, because too low rpm is actually increasing the fuel consumption due to inner friction of engine parts - in the end it is - as u said - very much dependent on the individual car, so better check it out yourself with the car computer...
and yes, there is quite a large penalty when going over 4500+ rpm fuel consumption may double then...
but again im not the expert in here for saving fuel - more for burning it kinda fast
