Wonder if anyone can help me here. I was gonna put the XL-4 Motorcraft supercharger oil but when I got in touch with the Kenne Bell customer support, they mentioned that I should fill up the supercharger with regular 50w engine oil. I was thinking if this is monograde oil or if I could use multigrade (5w50, 15w50) engine oil? its bluish-green in color. Any ideas?