Recently purchased 01 748... best thing I ever did for myself. Oil is starting to look a bit dark, need to change soon, wondering what I should use. Local dealer says Mobil 4T, but thats 10/40 isnt it? Dont I want 20/50? Mobil has that VTwin stuff, kinda leaning toward that, its 20/50, but dealer said 4T. Somebody shed some light. Thanks all.