Ok, I'm sorry I barely read any of the posts so I hope I don't repeat too much that's already been said. I'm going to major in a science that involves a lot of chemistry so I'm a big nerd when it comes to this kind of stuff. I always hear people talking about the propane vs. green gas issue so I have done an extensive amount of research and experimenting on this and have come to a not so surprising conclusion. I've found that green gas is propane based that is sort of infused with oil so that the oil to gas ratio isn't off and for every molecule of propane there is, there is a molecule of oil to back it up.
Also during this research I found green gas is highly synthetic which can gum up your gas system faster or slower depending on the amount you use your gun. The more you use that gun it actually helps to kind of auto-clean the gun, if you don't use the gun much than your gas system is going to gum up so bad you won't be able even pull the trigger.
Basically, green gas and propane mixed with a little silicone oil are the same things but if you use your gun extremely frequently green gas is the way to go and will probably save you in the long run. If you don't use your gun all that much, the cheap and easy way (propane mixed with silicone oil) is the way to go and your gun won't gum up very bad if let sit although if you go this route your gun will need more frequent cleanings.