Check out this website and chat. There's posts on using vinegar and other tips: http://ths.gardenweb.com/forums/laundry/ There's a lot of info about the Neptune machines and talk about using vinegar as a fabric softener. It won't hurt. I dont' know about the baking soda/vinegar combo. It probably wouldn't damage anything. But most people on that site talked about using bleach and hot water to take care of mildew/mold smells in washers.