Try adding 1/2 teaspoon of TSP to the laundry. It's terrible for the environment, but it's amazing for getting rid of ring around the collar type of icky.

Tsp was regulated out of laundry detergent in the 90's and dishwasher detergents in the 00's for i think for good reasons. I will soak some laundry in it periodically to get rid of body oils.