This weekend we are going to Kansas from Michigan and it's about 1600 miles round-trip. We will be pulling a trailer that is about 3000lbs empty. We will be towing a maximum of 6k lbs. The vehicle were using is a 2003 Dodge Durango with 250k roughly. My question is should we keep overdrive off the whole trip? And what mpg should we expect. Also I am getting the oil changed with 5w-30 and changing the oil filter and air filter. Spark plugs were don't about 2k miles ago. What else should I do to prepare for the big trip?