UOA for my F250 2006 6.0 (most reliable vehicle we've owned). Oil changed with conventional Delvac Super 1300 every 5k. I started to notice diesel smell at the last oil change, so I short changed at 3,100 miles on the sample. I used Oil Analyzers since Blackstone's testing method is not a reliable way to get accurate fuel dilution. 240k miles on engine and 3,100 miles on the sample.