when i was changing my SPF over to an all AN 12 (from AN 10) system, i had to cut and make lots of hoses, some several times. Used several different
oil filter mounts, so over several months, i drained a lot of
oil lines.
i was amazed at how little
oil is actually in the lines and oil cooler!
My guess is that an extensive AN hose/cooler system holds less than 3/4 quart in the whole thing. Trying to blow it out with air, then starting an engine with dry lines is more risky than i would want to take, to get out about 8% of my old oil.
By the way, i use a Griot's sucker system, just stick the plastic hard tube down into the dipstick hole, pump it about 10 times, go get a beer, and come back in a few minutes, (i slightly jack up the rear of the car to put the front of the sump down just a bit), and voila, in about 10 minutes, my engine is sucked dry. Never have to crawl underneath, and risk some misthreading or leakage at the drain plug.