Pulled a sample just to check after over 3.6 years on the oil. The previous oil change was 11/1/2013 and this oil change was done 7/1/2017 with 53,350 on the clock. The truck obviously sits a lot and is not driven in the winter. When I do get it out, it's for longer drives (Generally more than 50 miles round trip) so it gets fully warmed up. I was worried about going this long, but it doesn't appear to be a problem per Blackstone.