It depends...
For whites, I use a Miele set to 160F or 170F, and regulare scented Persil. I have not found it necessary to add fabric softener for this.
For colors, I generally use Sears Ultra Plus HE, with 33% STPP added. I dilute Downy 50% with water, and add about an ounce of that to the dispenser. I wash these in the Maytag Neptune 7500 at 105F for most shirts and 130F for most pants.
For bath towels, in the Neptune at 130F, I either use a mild liquid like Safeway Select Free/Clear HE, with no softener, or just plain STPP with a dash of concentrated surfactant NP-9, and with a very small amount of diluted Downy.
For heavily soiled work clothes, which often have machine coolant with foam supressant splashed on them, I do a pre-wash with 2 oz of Sears HE/STPP, followed by a long wash at 130F with more of same. Sometimes I find I have to add extra NP-9 to get a very thin layer of suds. The pre-wash is really a special warm (85F) rinse/spin cycle in the Neptune, since the standard Neptune pre-wash doesn't drain and I do want to get rid of the machine coolant before the main wash at 130F.
I have tried a lot of other different detergents and even grated natural soap, but I usually come back to the above products and formulations. The natural soap plus STPP actually works pretty well on things like bath towels, as long as sudsing is carefully monitored, and I might try that again in the near future.
