I've heard yes and I've heard no, it doesn't "sit right". According to my old boss you can subtitute argon for steel but not argon/co2 for aluminum. Argon for steel seemed to work all right when I did it but how does the weld measure up strength wise I wonder. If anybody's got the answer for this question out there I'd sure like to know. The guy who said you can't was selling the mix for more and I wonder if that had anything to do with it.