Some research would have landed you on this thread rather quickly http://www.airsoftcanada.com/showthread.php?t=6268
In short: yes. Green Gas is propane with silicone oil and scent impregnated into the mixture, with inflated prices. The propane adapter, and this discovery was all the brainchild of our very own MadMax, who runs AirsoftInnovations who also created the Tornado Grenade. 98% of us use propane in our gas guns, adding our own silicone oil (also provided by AI) in the propane tanks (small green Coleman tanks for camping from CT or Wally World), and the other 2% don't know about this and still use green gas at about 300% higher price.