Need to buy some shielding gas for my new tig welder. Call the local welding shop and the rep told me I could use CO2/Argon mix (the same gas mixture I use in my Mig welder). Is this true, the rep said he has never used a tig machine before, so I really had some doubts about his information. I need some advice on which gas to buy. The manual states Argon is the one for Aluminum, SS and mild steel. I will be practicing on mild steel and SS for right now, any help on the right gas would be appreciated....