Green gas is being sold for 8 bucks a can. Propane is being sold for 10 bucks for 4 cans 3 times the size. Thats the difference. All green gas is, is propane with some silicone oil thrown in so in so propane works just as good as green gas. All you need for propane silicone oil to add, and a propane adapter which costs $19.99 from Airsoft Megastore. Another point is that green gas is not sold at all sporting goods stores, while propane is sold everywhere. A false myth is that green gas lubes your gun as you shoot and propane does not. This is false because while using a propane adapter it actually puts MORE silicone oil into your gun that green gas does. So in conclusion the only con to propane is that it smells like shit. and you know it :)