CO2 tanks for paint ball markers DO NOT contain oil of any kind. The moving parts of the gun are oiled directly. And since the oil type varies from gun to gun, and some guns are destoyed if you use the wrong oil, it wouldn't make sence to have oil in the tank. In Canada all commercial sources of paintball, welding and fire extinguisher CO2 are food grade CO2. Its usually derived as a byproduct of corn based alcohol production here. Its the alcohol mixed with automotive gas...so loads of production. CO2 is a product of alcohol fermentation
The paintball tank adapter is avalible here from Badlands Paintball (
http://www.badlandspaintball.com/airsystems/hoses.html) for about $15 (or from a paintballers broken gun for less) A trip to an industrial plumbing or hydraulic supplier for a high pressure pipe nipple or adapters to fit any inert gas regulator. Be sure to use fittings rated to at least 1000 psi. The upside to paintball tanks is, we can get them filled at Canadian Tire or the paint ball places, 7 days a week till 9pm most days and its about $10 CDN. I was paying $15CDN to fill my 5 lb standard tank.
CJ