We currently have a 2011 Gen3 LTD with 5.4 3 Valve and HD Tow with 62K miles and a 2017 Gen3 LTD with 3.5 TT V6 and HD Tow with 45K miles. We had a 2014 5.4 3 Valve (same specs as the 11).
We change the oil / filter and rotate tires on both trucks every 4000 miles using only Mobil 1 Synthetic.
On the 11, we have changed brakes, rotors and shocks as maintenance items. We have also changed all of the HVAC actuator motors (dreaded clicking) as well as the brake ABS controller to correct pulling to right under very hard / emergency braking. Other than that, it has been a trouble free truck with no engine / transmission problems.
On the 17, we have had an ongoing issue with rear hatch window leaking when going through high pressure water such as a car wash, after 3 try's by dealer, it is much better but not completely corrected. We also had the brake master cylinder replaced due to failure (common problem on 17s). These were both handled under warranty.
We tow long distances (900 to 1300 miles) with the 17, pulling an open car trailer weighing either 6300lb or 4900lb, depending on the vehicle. We have had no engine or transmission issues to date and can say it is a pleasure towing with this truck compared to the 5.4 because of the increased HP and torque.