I have a Bernina 440QE, and I have used all kinds of thread in it successfully. If the dealer had told me I could only use Mettler I would have found another brand of sewing machine to buy. I love to use Bottom Line in the bobbin, and I mix threads top and bottom all the time. I no longer buy Star thread, because I've found that CT is better quality and cheaper too. But I'm still using up the Star brand, as well as the leftover Coats & Clark and some old spools that I had left over from sewing when I was in high school and college (and that was a very long time ago). I figure if it isn't rotten, I can use it for piecing. I do clean and oil the machine frequently.