I recently picked up an 83 Honda CB750SC, 750 cc inline 4 cyl, air cooled, shared sump with a wet clutch. The owner’s manual specs 10w40. From my research here running a 15w40 diesel rated oil would be a good choice for my application. Between Rotella T and Delvac, both of which are easily obtainable to me, which would be the better choice?