Not try to say one is better. I get amsoil for my dad with my perferred customer discount. He likes the amsoil because of the discount i get. He gives me a list of oil he needs for oil changes 5w30 for his f150 and 5w20 for his malibu. Sometimes i cant get to the supplier before they close because of work so when pops come to town and i dont have oil i get the usual " what have you been doing all week?" He live about 2 hours away. I told him just pick up some other synthetic oil but he likes it when i get him amsoil. They live in a small community and walmart is there along with all major auto stores. So if i tell him run to walmet and pick up some penzoil ultra or ultra platinum that should on the same level as amsoils xl line if not maybe better? Just want to make it easier for dad to get oil when i cant get my " special never heard of once in a life time" discount he thinks im getting. Oh yeah he wont sign up,for the perferred customer, i think he just likes having me get his oil.