I've learned enough from here and YT so that I will feel good about adding leftover new oils to my Ford Fiesta in 2020 when I do my next OCI. I have about 1 quart of leftover PYB 5w30, and about 1 qt of NAPA 5w30 SB, and will add 2 qts of Super tech 5w30 FS. That's going to be my oil cocktail, with a new Fram PH3614 filter. I'm anticipating the coming of that great day, LOL. I was actually going to recycle the leftover oils until I saw how some of the engines fared better on cocktails like this than they did with one type of oil.