Orings are easy and cheap to replace. I'd rather not use silicone grease to protect non-anodized threads..
It works fine and I've yet to see a o-ring damaged from it. Used it for years in fact. Also on the o-ring.
I'm a engineer by trade and honestly I don't thinkI've ever seen an o-ring damaged from oil. But then again maybe that is because the ones we use in the field are specificly for the application they are used for.
+1 I've been pretty happy using the same oil I lube my bike chains with - ProLink or Chain-L No 5. Pretty sure these are just synthetic motor oil with varying degree on mineral oil used to cut viscosity. I also have some shredder oil that works pretty good - very light and clean. Right now I'm testing 3 different oils and SuperLube grease. So far I haven't noticed any damage to the o-rings.