Cruise RPM setting

Since you're building time, why wouldn't you fly at the lowest fuel
consumption settings you're comfortable with that are consistant with
the POH?

You log calendar time for logbook purposes, and done correctly at low
RPM and well leaned you'll really cut back on fuel. In our Mooney,
which gets pulled around by an IO360, we often cruise at 1950 RPM --
allowed in the POH -- and fuel flow is in the 7 or 8 gph.

As an owner, we like low RPM as well, since that extends the real time
between overhaul -- tach hours assume 2400 RPM or so.


, On Oct 13, 11:16 pm, john wrote:
Shortly after getting my private license I went to a different FBO and
got checked out in their aircrafts - C172 and Piper Cherokee.

I talked with the CFI and asked what RPM settings he would recommend.
I'm renting dry, so one way to reduce cost is to slow down and thus
save fuel. At the present time I'm just building hours towards my
commercial ticket. Rarely am I in a hurry to get anywhere. He
mentioned that if I needed to get somewhere quickly, to keep it around
2400. If I'm just building time then to reduce to 2300. It will save
fuel as well as reduce the sound level.

The CFI no longer flies out of that airport, so I don't have contact
with him. I'm interested in others opinions related to rpm settings.
Is there any harm to the engine with reducing the RPM even lower, say
2200 or even 2100 RPM. I will confess to bringing it back to as low
as 1800 for a short X-C and found it to be good slow flight practice.,
which gave my one leg a work out in order to keep the bubble in the
middle. I wouldn't want to make many flights at 1800 though.

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

Thanks,

John