I bought this truck in Missouri, and put about 1000 miles on it before doing the first oil change. I don't know the miles or type of oil in this drain interval, but will be doing more oil samples to settle on a change interval. This truck has EGR and DPF emissions controls, so I was worried about soot and fuel dilution in this sample, but those readings are OK. TBN was still very strong. The previous owner seemed to be running an oil with decent anti-wear content: 173 Boron, and 1023 Phosphorous. I also just changed the trans fluid last night, and the drain oil looked new. Maybe the truck was maintained conscientiously. I put in a fill of Delvac 1300 Super, and have made some trailer deliveries in the past few weeks. The maintenance minder is already signaling for an oil change in only about 5000 miles. Cold weather has set in, and I have been idling the engine overnight, and there have been many regens. I think I'll extend to about 7000 miles, then take a sample to see how fuel dilution is. So far, I'm not impressed with the fuel economy. I haven't done better than 9 mpg towing trailers that I used to get 10-11 mpg towing with my old truck. Running unloaded, the new truck hasn't done any better than 17 mpg, whereas my old truck was getting 21-24 mpg. On the plus side, the new truck has lower cab noise, and rides a lot better, so I'm less beat up at the end of the day.