What oil to use
Ok here we go, yes you can run diesel oil's as long as they are rated CF-4, CG-4, CE, CF. Most diesels run a 15/40 weight oil in them. I know because my personal truck is a FORD Powerstroke Diesel. I run AMSOIL series 3000 5w/30 diesel oil in it. Diesel oil's are made to combat a soot problem that diesel's have. If you want to run that type of oil in your Harley, go ahead, but I wouldn't. I'm not going to get into an arguement with all of you over which oil is better than another, but I will say, stay with oil's for your Harley, that are formulated for motorcycles, they have a sling additive in them and are made to run all day at oil temp's. in the 200 deg. to 240 deg. all day long. Also I have put AMSOIL 20/50 in several of my customer bikes without any more engine noise.