Jellycopter, The R-Nav fuel page takes into account the wind, as it works off groundspeed. These days, even with more regulated airspace above, I often change altitude, as much as is reasonable, to gain the odd knot or two of groundspeed.
Gomer,
I think the S76 was what the OP was referencing. The first limit at higher altitudes is often Vne, not any engine or transmission limit, so you are forced to operate at reduced power settings. This can account for at least some of the lower fuel requirements. At 6,000 ft, you have to bring the power way down to stay below Vne.
Yes, but on the other hand you have the IAS/TAS relationship to your advantage with increasing altitude so it's not as bad as it might first appear from "raw" numbers on the Vne placard.
