I've been doing so MORE reading about oils. I'm going to try out the Mobil 10W30 since I have found a local oil company that can get the oil. It's not much of a cost savings overall. It's more about seeing if it makes any real difference in the motor. I'm a firm believer in your motor tells you what works and what doesn't work. I don't really care to run samples since there's TONS of posts about 10w30 oils doing good in the 6.0L. The link below is off the Mobil site.