Since nobody has answered.. A bit of googling produced the following figures for fuel consumption and typical cruise speeds. Some sites gave very different figures for same aircraft so might be errors....
Rotary:
206B Jetranger - 30 gph, 110kts
R44 - 15 gph, 115kts
Fixed Wing:
C172 - 10 gph, 110kts,
Piper Seneca - 22 gph, 175kts
So looks like the C172 is probably the lowest.
PS: I estimate the lorry burns 7 gph and cruises at 48kts but obviously that's carrying 38 tons where as the above err don't.
Last edited by cwatters; 27th Sep 2009 at 20:24.