Odd thing that I notice is the extreme fluctuations in airspeed while in cruise:  5 - 8 KIAS in smooth air with no changes to power.  Auto pilot on (with altitude hold), and Fuel flows, MP, RPM, EGT... don't budge, but

KIAS moves up and down 5 to 8 knots...

Matt,

 

Thanks for the trip report -- some just don't want to go smoothly.

 

I have seen similar variations of speed in smooth air.  I think that was one of my problems in hand flying and holding perfect pitch.  When I have had Arnie flying along side, I occasionally gets comments like "Why'd ya slow down?"  As you have seen, there is no indication in the engine data.

 

Are we marginally losing laminar flow from time to time?  Have others noticed this? And, the ever imponderable, "Why?"  Does it happen in a certain speed range? Altitude? Bug contamination?