I use our frying oil for liquid utility soaps. I make liquid soap using the Failor method, so I have an actual KOH excess (before I neutralize). This means there are no extra fats in the soap, all that cooking oil (plus the CO I also add) are completely saponified.
I really like recycling the used oils this way. My DH does not like to re-use any deep frying oil, so they are a one time use oils. I know exactly what went in there and it is all fine with me. Also, I filter all the recycled oils I use. The soaps work great and even the unscented ones smell OK. DH prefers unscented for laundry, I do scent the liquid soaps I use for dishes. I have used soy a lot, recently we switched to only peanut for deep frying, so I am also using that. Peanut oil (recycled) and coconut oil (new) make a very good liquid utility soap!
I have also used recycled soy oil for CP soaps. I still have one of the bars of soap I made this way about 20 months ago. No DOS, and I have gotten DOS from 'new' oils, mostly soy. I was probably just lucky, so I am not doing this for CP soap anymore, but in a pinch it will work. Just use it sooner than later...