oiling air tools keeps the water out. especially in a shop, you're never gonna get clean dry, 90psi regulated air. its going to be dirty nasty wet air at 130+psi.
i lube mine up with a mix of cheap airtool oil, motor oil, and some atf

it just needs a thin coat to ward off rust from the watery air, and keep the air motors clean and mobile. ive used snapon air tool oil before, and hf, and CH oil. anyone who says they notice a difference is lying to you.
i lube my ratchets with whatever amount of motor oil inevitably drips on them. wipe off the exterior and you're good to go. the big thing is that you dont want to clean tools with solvents or submerge them in gas or anything like that.