You won't be able to find pure silicone oil from just anywhere. Even Airsoft Innovations has to buy it by the barrel from suppliers. Machine oil used for sewing machines, air tools, etc typically contains some type of petroleum distillate as well as other additives. Typically, this type of oil is NOT silicone oil.
In North America, it's special application. If you go to Canadian Tire and ask for "Silicone Oil", they'll give you a can of this stuff that will eat your o-rings alive. It's called "Silicone oil", and is used for keeping gaskets and window seals moist, but it will also swell them up and break them down with time due to the petroleum distillates present in it. It can also break down the plastics used to build the body of your gun. Even if the can does not state it contains petroleum distillates, the easiest way to tell is by the smell of the fumes that come off it. If it smells like a solvent, chances are, there are petroleum distillates (please don't inhale directly. Use the "wafting method" taught in high school chemistry class!)
Just so it's clear, the silicone oil we use is primarily NOT for lubrication. The main purpose, is to prevent the o-rings and rubbers from drying out. It keeps it moist. If you make it too slippery, things like the hop up rubber will not function properly, and you'll get problems such as dirt attraction.
Whatever it is that you find, just make sure:
1) It does not contain ANY petroleum distillates
2) It's ultra light weight... roughly 1.5wt would be what you're looking for. Anything thicker, and you will create a huge mess in your gun.
The best places to find something that meets these requirements and almost guaranteed to not affect the plastics/rubbers in airsoft, is at your local hobby shop that sells remote control cars. Ask them for "Shock oil". It's used to control rebound rate in suspension systems for RC cars. I'm not sure if it can be found in weights as light as 1.5wt, but check it out to see what's available. The last time I checked, the lightest I found was 2.5wt.
Check out the prices... it's most likely cheaper than airsoft-specific silicone oil found through ASC retailers, once you factor in shipping costs. But just so you have a reference, I sell a 50ml bottle for $6.
Last edited by ILLusion; October 29th, 2010 at 10:39..