Still towing travel trailers. Some in mountainous terrain in warm weather. 11k miles on this oil fill. Added particle quantifier and truck hourmeter readings to the new UOA. Polaris comments: Flagged data does not indicate an immediate need for maintenance action. Continue to observe the trend and monitor equipment and fluid conditions. OXIDATION is at a MODERATE level, which may be due to extended drain interval or high operating temperature. Viscosity is MODERATELY HIGH. Causes include contamination, oxidation, incorrectly identified viscosity grade, or adding a different viscosity grade to the component. VISCOSITY INCREASE may be due to lubricant oxidation. Please provide missing application and sump information. Lubricant and filter change acknowledged. Still have lubricant oxidation, despite having the crankcase ventilation filter and EGR valve replaced about halfway through the OCI. Maybe it could be that the oxidation occurred before the repairs were made? Adding the Redline oil supplement didn't help anything, either. KV100 has once again increased out of grade, just as much as before, and on a shorter interval. I think the oxidation occurs early after an oil change, then slows down. The UOA at 182k had oxidation of 28 on a 20k mile interval, and the new UOA at 226k has oxidation of 23 at 11k miles. Soot is safe at 1.7. I think I will continue with 10k OCI's, and keep the filter in for two intervals. I have run Fram Ultras for 20k miles before without trouble. TBN was still strong. 14k miles seems to be the limit for TBN. Will continue searching for a reason for the oxidation. Currently have Motorcraft Super Duty in it, which is a syn blend, so I don't expect it will do any better than RT6. I have also disconnected the EGR valve to minimize EGR. Maybe it will help, but I can say that drivability has immediately improved. The engine no longer stumbles on every gear shift.