Additional Lycoming Information
Lycoming IO-540 Operator's Manual (Part No 60297-10 – 2nd Edition – July 1982)
This is an old version. The most recent version (60297-10-3 of June 2006) was not found online. Refer to the Lycoming Support for latest revision information.
Lycoming Service Instruction SI-1094D (25 March 1994)
Instructions about usage of Lycoming Engine
Lycoming IO-540 Operator's Manuel Extraction (Fuel Consumption – Performance)
However undated, these two graphs provide updated info on consumption and performance
Leaning Procedure
It is highly recommended to read the ’Lycoming Flyer Key Reprints‘ Manual.
Especially the section on ’Proper Leaning at Cruise Aids Safe Flight and Saves Dollars’, found at page 39 of the ‘Operations‘ Chapter.
N123AX is to be flown at Peak EGT, even at low altitudes (and already reducing short after takeoff). In this way, no confusion exists if you are flying at the rich vs the lean side, but especially consumption will be minimal.
My experience during the last trip around Southern Europe dictates fuel consumption, if properly leaned, varies between 13,5 and 15 Gallons/Hour, nearly independent of the altitude (let’s say between 3.000 and 10.000 ft)
Please also refer to ’The “New” Old Leaning Technique‘ for further reference.
Also, when preparing for descend and landing, avoid sudden cooling of the engine (cf. page 53 of the ‘Operations‘ Chapter)
Further, there’s an article on EGT and combustion analysis to read as well.