I have been trying to understand the exact details of an EGT gauge, specifically to understand why on a recent flight it was (for a short time) reading much lower than I would have expected.
I would usually reference the EGT gauge during leaning, and from experience of the aircraft, am aware that peak RPM usually coincides with between 1400-1500 °F. This is a useful cross check, and reference during leaning.
During a flight yesterday the EGT was reading about 1200 °F when leaned just rich of peak. This felt unusual, and I wondered if there might be something amiss. The OAT was around 10°C (50°F) degrees, and I was in a thin layer of cloud at the time.
Some 20-25 minutes later I was clear of cloud and the EGT was reading 1400 °F which is more what I might expect.
Is there any obvious reason for this?