We use Aeroshell 15W50 in all six of our Lycomings. It has the
additive recommended by Lycoming for the cam/lifter life. The
straight-weights don't, as far as I know.
We had cam trouble some years ago with another brand that didn't
have that additive. Might have been the lack of additive, might have
been the oil itself, might have been a bad cam. It was in an engine run
hard almost every day; corrosion wasn't a factor.

Dan