My pressure switch is set around 175-180....
The oil passes with the compressed air that comes out, thats why you have to keep it full..... The closer to vertical that it is mounted, the less oil blowby. BTW..... i managed to blow a SS braided line at the crimp for the fitting with my york.(it was a leader hose off a viar that i had killed already) I think the built in check valve went bad or something. :dunno:
EDIT: You can get a coalescing filter for the oil that gets blown out of the york
i run mine at 300 psi and it gets cycled about 3-4 times a day if not more. i didnt do any oil mods to this one, just slapped it on there and let it pump. i have the intake side ran with a 5/8 hose to the inside of my air cleaner so i dont ever need to mess with a filter unless my engine needs a new one. im running a stainless line all the way to the tank too. it needs to be alot bigger than somthing off of a viar, like 3/8 ID or bigger. oh yeah, i also hooked up the original a/c fast-idle selinoid to the clutch so it pumps up quicker.