I'm not a big fan of
"I don't want to know, and I don't want you to know either". Those posts are not helpful.
Oil companies list their oil specs in hand books and on web pages, so you can spec it for yourself. Periodically someone does an independent lab test of several oils at the same time. That takes a bit more searching, but it's worth the time.
Oils are reformulated all the time, including Aeroshell. They have to because oil base stock changes from day to day. Addetive packages change because of this as well. (blended whiskey comes to mind, made to taste)
New automotive oils have less ash (or ashless) because ash damages catalytic converters, and leaves deposits on piston crowns. So the latest oil spec is probably more acceptable to your aircraft engine.
If you were low on oil and the FBO was closed, but the auto parts store open, I don't think it would do any harm to add a few quarts of 20-50, or 15-40 and fly home.
As for cost effect, oil at the auto parts store is not very cheap these days, certainly not 1/3 the price of aviation oil for the quality of oil you might find acceptable.
As for lead scavanging, 100LL does not have very much lead in it anymore, and most of us change oil @ 50 hours give or take. Many of us have oil filters on our engines, so a detergent oil theoretically would be called for?
It Is worth discussing.
I use aviation oil in the Cessna, automotive oil in my RV-8, but then again, it's got an auto engine.