"Thomas Borchert" wrote in message
...
John,

n the 172 I have reduced fuel from over 7.5 gph at 2400rpm to about
5.5 gph at 2200-2300.


First of all, the power settings in the POH mostly make a lot of sense.
Secondly, if you pay by Hobbs time, many people use what is referred to
as "rental cruise", aka full throttle full rich. You probably save
money by that, the rental outift probably won't.

Your objective of saving fuel and prolonging flight time is unusual for
a renter. Still, if I were to build time with a rental aircraft and
cost would be the same regardless of power settings, I would GO to
exciting new places at the fullest speed available rather than dawdling
around in the area I know. With respect to time building for a
commercial, that tactic would be immensely valuable since it would
expose you to new terrain, different weather and unknown fields. So,
again, if cost remains the same regardless of power setting, IMHO you
might want to rethink how you build time. I would even suggest a
multi-day cross country to an area of the country you always wanted to
go to.

As a general rule, I normally use the maximum recommended cruise power
setting from the POH, since I normally want to go somewhere. That's
mostly 75 percent. I use best economy mixture if I have a tail wind and
best power if I have a headwind. Also, I use as low an RPM setting as
possible for noise reduction, but I have a choice, since my airplane
has a constant speed prop.

--
Thomas Borchert (EDDH)

Remember, he's renting dry.

Admittedly, that has been a little unusual for some time; but, with
fluctuating fuel prices, who knows?

In addition to asking the owner, I would ask around the local flying
clubs--since many flying clubs have tended to operate their equipment in a
similar manner.

Peter