My dad used to service hospital equipment, including their washers and dryers, and you wouldn't BELIEVE some of the stuff I've learned from him over the years.
The first thing someone should be telling people is to
NEVER use powdered laundry detergents at all! They're
bloody dangerous!
While liquid detergents have many of the same cleaning agent chemicals in them, powdered ones have all kinds of additives and chemicals added to those to granualize the liquid suspension of the chemicals. You should always try to use liquid detergents--not just laundry, but dishwasher, etc, and if you can't get liquid, use the gel ones.
Something else that they don't tell you is that all laundry products are FAR, FAR too concentrated, and were even before the current "lots of loads in a little bottle" marketing strategy that's made it all about "10 loads in an 8 ounce bottle." These poor puppies wouldn't have such severe chemical burns if the products out there now weren't "ultra" powders that concentrate the chemicals into ever smaller amounts of binder!
You should know that you can actually damage both your machines AND your clothes if you oversoap as a regular thing. Most laundry detergents have a "fill line" in the cap that is about 1/4 cup of soap. That's 2-3 times as much soap as you really need, unless you're cleaning barn clothes or something. The easiest key to tell if you're oversoaping: If there's a layer of bubbles when your clothes are agitating, you've used too much soap. There should be bubbles, but they should be scattered across the surface, and should be few in number. A layer of bubbles is bad. If you use a laundry aid like Oxyclean or a water softener like 4 Kings, you may need as little as a TABLESPOON OF SOAP for a normal load of laundry!
NEVER use a dryer sheet. They have a stiffener in them that's chemically related to fiberglass, and again, will damage both your dryer and your clothes over time.
In terms of liquid softeners, a regular softener should be diluted by at least half, and a 1:2 dilution is preferable. Clothes will be just as soft and have just as good static control, but cause less drainage/backup problems and fewer incidence of rashes. Ultra softeners like Downy should be diluted 1:5 or 1:6 at a minimum. I personally dilute 1:8 and my socks don't stick to my towels.
Just call me Laundry Girl....