School me on Air Compressor Maintenance

[whateverpratt]

I've been hobby wrenching on cars and trucks on and off for the past 20 years, and I finally got an air compressor. I picked up an old (1963) ~20gal air compressor super cheap. It works great.

What do I need to do for maintenance on this little sucker? I seem to remember people talking about draining them every now and then, and I'm guessing the compressor oil should be changed every now and then.