From what I remember, I think piston planes use a non detergent oil.
Not sure about the zinc.
Interesting question. I think it deserves a look-see.
GT
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Looked into this a little more in depth this morning and you're right GT, most of them are non detergent oil or ash-less dispersant oil. The Phillips 66 oil doesn't have any zinc in it, I'm not sure about the others but I assume they are the same.
After looking into aviation piston engines a bit more they are built to run on zinc-less oils. Now a lot of the newer light sport aircraft and home built stuff use subaru engines or rotex engine which are designed to be used with automotive motor oil. Shell makes an aviation grade oil designed for these engines but it's about 10 bucks a quart, might as well stay with vr1 or something similar.
I did find this page where someone tested a bunch of oils which is pretty interesting.
http://speedtalk.com/forum/viewtopic.php?f=1&t=35836 Sent from my iPhone using SoCal Jet Boats