The three most popular dino oils for diesel engines seem to be Rotella T, Delo 400, and Delvac. For at least three years now, I have been using Rotella in all five of my diesel engines (a Mercedes, a Ford Powerstroke, an International Harvester tractor, and a Kubota lawn mower), so it came as a disappointment to see more than one person in this forum say that Delo is so much better than Rotella. Can anyone make a good argument why I should not switch to Delo? I hate to switch brands that way, but if Delo is really better, I suppose I should.