Lisa, the reason for a relatively high RPM for a few minutes just before
shutdown is to help prevent lead fouling of the spark plugs. Lycoming engines
tend to run too cold at low RPMs to keep the lead salts from avgas burned off
the plugs.

Best regards,

Steve Robertson
N4732J 1967 Beechcraft Musketeer (Lycoming IO-360)

Roger Long wrote:

1800 is better (with the leaning mentioned above) but you won't make any
friends in the tiedowns using those RPMs. We've found the 1200 to be
sufficient.

--
Roger Long

Dan Luke wrote in message
...

"Lisa" wrote:
The POH says throttle full aft, then mixture cut-off to shut
down.

Which is best?


According to Lycoming Service Letter L192:

"Prior to engine shut-down the engine speed should be maintained between
1000 and 1200 RPM until the operating temperatures have stabilized. At
this time the engine speed should be increased to approximately 1800 RPM
for 15 to 20 seconds, then reduced to 1000 to 1200 RPM and shut-down
immediately using the mixture control."
--
Dan
C172RG at BFM
(remove pants to reply by email)