I just don’t.
Unless it’s kitchen towels covered in grease, or really muddy, greasy clothes in the load, I don’t bother.
It comes out smelling fresh and is perfectly clean without that horribly over-perfumed scent of fake flowers or fake mountain breezes.
The agitation, and the warm water does the trick, and I have never looked back since.
I did try a load here at my parents, with a bit of detergent and I almost threw up from the nausea of the strong chemical-laden ocean mist scent that came off the clothes.
I have to re-wash them later on. This time, sans detergent.
I don’t do it because I’m cheap, eco-friendly or that I want to save a boatload of money.
I do it, because it has made a slight difference, for the better to stop using detergent. My clothes seem to last longer/better without chemicals attacking the fabric, and the fresh-without-being-nauseating scent is a huge bonus for my (now) sensitive nose.
So unless you are covered in grease, huge chunks of dirt, and/or feces on a regular basis, give washing just with warm water and a cold water rinse, a shot.