MIG welding gas, What do you use? Options

[obscurity]

I did a search but didn't find much. What gas are you using for your MIG welder? 100% CO2, CO2/argon, or 100% Argon?

Just Curious,
John W.

[LvSteveH]

Good advice so far. A few other points of interest:

CO2 is stored as a liquid, and will last much much longer than an equivalent cylinder of 75/25 shop mix which is stored as a gas. The cylinders are not compatible.

As noted, CO2 will typically give more penetration. I agree that 75/25 is a little cleaner, but you can make very nice welds with either of them. It really depends on what you are doing. For most automotive fabrication which is typically thinner material with less deposition, I'd go with the 75/25. If money is tight, then there's no shame in using CO2, it's perfectly acceptable.

Some guys will actually refuse to run CO2 which I just don't get. A good welder can make great welds with either gas, and a bad welder is just as likely to make bad welds with either of them.

I actually have a bottle of each. I generally use the 75/25, but if I run low, the CO2 is always there and it seems to last forever. I can guarantee that even an expert would be hard pressed to tell the finished welds apart. The characteristics are a little different, but once you adjust for them, it's business as usual.

Good preparation, free of paint, oil, undercoating, and rust will make much more of a difference than the type of gas. The extra time it takes to get down to nice clean metal is worth the effort.