hey fellas! did a complete service on the Titan recently; fuel filters and oil filter/oil change (5w-40 Premium blue). had to take my Pace enclosed trailer and Lotus up from Elkton MD to Newton NJ to have the recently rebuilt race crossflow motor installed. since I wasn't going to a race the trailer was lightly loaded (prob only about 6k lbs). round trip was 312 miles. fuel mileage this trip was the best I've ever seen it; 13.8 on the truck computer and 13.4 hand calced. I do always run Optilube additive if that matters. I think that a huge factor in yesterdays fuel economy was that I kept it right at 65 mph (there was fairly high cross winds too FYI) on the highway, which was about 2/3 of the total mileage. the other 1/3 was back roads at about 40-50 mph. on the way there i did get caught in rush hour for about 30 mins with stop and go crawling of 5-10 mph (that probably hurt the fuel milage). there's no doubt that 65 seems to be best for towing fuel economy with our gearing (that's like right at 1700 rpm on my truck with the PR 20s). thats a good compromise of being solidly in 6th gear but not going so fast that the wind resistance of my big 8.5' square tall box makes too much drag. (plus with my trailer I try to keep it at 65 max so that i minimize blowouts. at 70-75 sustained is when i get ALL my flats in the past. anyway very comfortable tow through the large rolling hills and the Cummins seems to be breaking in more and more now. i love this truck for what i do with it!