How inefficient turbines are down low

Well, that's 4.8lb/min vs 6.17lb/min. How much does the climb out affect a turbine fuel consumption? It's a very short flight, after all. Would be interesting to compare a longer flight at lower altitudes, although I remember the fuel flow on our flight from Girona to be drastically higher descending into Nantes than it was at FL 270.

What software tools are used for the planning and how do they work?

Flitestar supports that sort of thing, I recall, though I never used any of those features. I vaguely recall there was a Corporate version which had extra support for that stuff, too.

And Jepp do a very fancy software tool, whose name I forget, and whose price was 5 figures.

Obviously one needs to get this right because the penalty for getting it wrong is pretty big. A landing just for fuel could be a huge hassle in other ways, if it pushes you into €xxx handling costs or hotel costs.

Whereas on a piston engine, operating peak EGT or LOP, there is very little MPG change once one is WOT i.e. FL080+ and it starts to get worse again when one has to go to max power near the ceiling e.g. FL170+ and even then the drop is perhaps 10%.

Also, economical flight at c. FL250-300 is done much closer to Vbg than piston GA flies at, so the MPG is much more affected by the weight, so one doesn't want to carry too much extra fuel. Whereas on a piston plane it makes almost no difference - of the order of a few % max.

Essentially you always go high. For a 1hr flight you go to FL280. I just use rocketroute. It has climb/cruise/descent profiles

So you reach FL280 just in time to start requesting your descent clearance?

I've done a few short hops with our jet, 43 nm, FL100, pulled back to 220 Kias, still burn about 350 lbs total for an 18 minute flight. They're mighty thirsty down low. When on the Caravan we used to operate it at about 300-320 lbs/hr at FL100 (Set by Tq and rpm at 1600) which would return about 160Ktas. Not very efficient, but we rarely had an incentive to go high.