STP oil treatment (Stay Together Please) is still out there !!

Wait until you try to take one apart that is so coked up you can't get the oil pan off & when the valve covers are removed there is a perfect mold of the underside. I'm not kidding, I was commissioned to rebuild a 302 Ford for a neighbor. I asked her about it, she was an older widow & her response was, "I never knew the oil needed to be changed, my husband took care of all of the car stuff when he was alive".