Oil is not Oil. There are as many "blends" of crude as there are oil fields (about 160 blends according to wikipedia https://en.wikipedia.org/wiki/List_of_crud

Oil is not Oil. There are as many "blends" of crude as there are oil fields (about 160 blends according to wikipedia https://en.wikipedia.org/wiki/List_of_crude_oil_products https://en.wikipedia.org/wiki/List_of_crude_oil_products). Some are "thicker" than others and that results in different products you can get from the crude you refine. Also, each crude requires a different setting in your refinery, and it is very costly and lengthy to change that setup. Refineries in the US are for the most part set to heavy crude. Guess what kind of crude the US get's from fracking? . . . It's not heavy crude.