I've got a Husky Air Compressor similar to this one:

http://www.homedepot.com/catalog/productImage/542762b4-a8aa-48b7-8240-d99a8187e2e8_400.jpg

Can I just use plain old motor oil in this? I know you can buy the Husky brand oil but have heard of people using 5W30 motor oil.

I use Mobil 1 5w-30. I have the same compressor.