"Aeroshell 15W50 has the Lycoming-recommended additive to protect
the cam during dry starts. It has served us well.
The cam gets enough splash off the crank once the engine's running.
It's coming off the sides of the main and rod bearings."

Dan -

From what I have seen inside Lycoming engines (and that's not very
many although they are all very similar) a small amount of leaking oil
from crank or rod journals isn't going to impact the cam surfaces very
soon after a really gooey & sticky oil startup. I suspect the cam is
going to have to rely on the residual oil from the last shutdown, for
some time - maybe even minutes for a difficult cold start - until an
oil fog environment is established. Laying a crankshaft next to a
camshaft & looking at the axial alignment of the two, The likely
initial oil splatter patterns look to me like they would miss the cam
surfaces.

A really interesting test would be to cut a hole in the side of a
junkable crankcase and examine the startup spray pattern.

Obviously you are doing something right. We both use the Shell
15W50. I've run counter to one of your "secrets" though in that I've
had a lot of short flights over 31 years to get to 1700 hrs TTSN on a
still solid Lycoming O-320E2D, only being religious about oil
preheats.

Maybe the presence of residual oil is more critical - in which case
the need for preheat would greatly increase for an aircraft sitting
for a few days. Might that jibe with your experience?