CurtainTwitcher
In general I find I only burn half the holding fuel by descending to say FL250 vs continuing at flight planned cruise altitude then entering the pattern to lose the same time.
Huh? You just provided figures that show 1% or less burn difference at holding speeds between cruise altitude and FL250.
Additional fuel (up to 5% as per your figures) can be saved by flying in a straight line vs a racetrack hold. Vectors (if they are long ones) will consume less fuel than a holding pattern due to less turns. Turns burn more fuel (more thrust required to maintain speed).
So, yes, descending early and slowing with vectors will be slightly more fuel efficient than maintaining cruise and entering a holding pattern.
This saving will be something less than a theoretical maximum of 6%, as some turns are still required with vectors. Not "half the holding fuel" as you claim.
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So, to the ATC'ers wondering which we prefer - the fuel savings are small so our answer may depend on other more significant factors which will change from day to day.
Such as:
1. Turbulence (why would I want to leave smooth air early?)
2. Icing
3. Workload (yours or mine?)
4. Fatigue (what's easiest?)
5. Personal preference of the pilot flying.
6. Personal experience of the pilot flying (e.g. first time in Oz? or fly 4 sectors/day out of BNE?)
So, if you have time, yes please ask our preference. I often request an early descent if it means achieving a short delay without vectors, but I won't if I suspect turbulence at lower levels, and I might not for a longer delay because vectors/holding is inevitable regardless.
Thanks for the explanations guys. Most of us get it, and most of us appreciate you are doing a great job with the resources and systems available. And yes, ATFM has helped quite a bit.