Okay, ground truth:
I drained exactly two quarts and set the car back on its wheels. Stick read exactly one quart down. I put one quart back in and waited; stick still read a little low. Ran the engine for a minute, let it sit for 10. Stick read at the low SAFE line. Put in half a quart more, ran engine a bit, waited - Stick reads exactly one-third into the SAFE range.
So yes, my engine does take 10+ quarts on a change, and as nearly as I can tell, the dipstick is reading accurately. (I would ass/u/me that Joe Lapine would provide the right stick, and that its reading in the SAFE zone all this time while showing no signs of
oil problem indicates that the SAFE level is correctly spec'ed.)
I'm going to drive it a bit and check again, then bring the
oil up a little higher in the SAFE range before I dump the rest in recycle. And next time I'll remember that and wait before I put in the last quart.
Then I have to tackle this fraggin' fuel drip from the pump... *sigh*.