I would recommend against using Aeroshell 15W-50, Aeroshell W80 Plus, Aeroshell W100 Plus or the new Phillips Victory 20W50 in a big bore Continental, as they both contain the “Lycoming additive.” This additive is required in the infamous Lycoming O320-H2AD and a small handful of other Lycomings due to rust causing extreme valve train wear. This additive contains triphenyl phosphate (TPP). TPP can create phosphoric acid, which can attack seals and magneto cushions. In the big Continentals with the starter adapter, the phosphate can form on the spring in the starter adapter, causing it to slip. As long as the starter adapter is in good shape and you have a well-charged, high capacity battery, this shouldn’t be a problem, but otherwise it could be an issue for your starter adapter. For these reasons I have switched to the regular Phillips multi-vis 20W-50 without the Lycoming additive (I made the switch after reading an excellent, recent Aviation Consumer article written by Paul Millner, a retired oil company technical expert, who provided the above info).

The OP also mentioned Aeroshell 120, which is a straight mineral oil, and barring manufacturers’ recommendations otherwise, should just be used for break-in. On the other hand, Aeroshell W120 is an ashless dispersant oil without the Lycoming additive, but it is only suitable for warmer climates (above 79 deg F).

I think kg summed it up best by citing 14 CFR 33.39, which basically says the engine has to fly with half the specified oil quantity, which is the technical justification for most of the comments saying 8 quarts would be fine. I’d let it run down that low and figure out what quantity the engine is happiest at. One caveat – be certain the dipstick is correct. During an oil change, I usually add 10 quarts, but my dipstick says I have more than 12 quarts.

I guess my 470K is pretty unusual--
I put in 11 quarts at oil change time & the dipstick reads 12.
I figure there's a half quart or so that doesn't drain out, so the dipstick is off a tiny bit
I generally put in some oil (less than a quart) about 15 or 20 hours into it,
then by the time it's ready to change at 30 hours its reading a bit low again.
So I figure it burns about a quart in 30.
Not bad for 1700 hours.