One time in baking soda, a second time in white vinegar.
One cup, warm water setting, right in the top-loader with the load. I do a pre-soak and an extra-rinse each time as well.
Works especially well on my white and light color towels instead of detergent in my experience.
At current prices at Sam's Club the cost is about 52-cents for the two loads, about 33-cents for a cup of baking soda for the first load, and 19-cents for a cup of vinegar for the second load.
That's more expensive than using, for example, ALL Free and Clear and CLOROX 2, which are about 13-cents and 21-cents in just one load, respectively, or 34-cents total. And water is money, too, unless you have a well like me.
But I like the results better.
Disclaimers say check to see if your machine is compatible with vinegar.
