I live in Oklahoma City but have been working in Dallas for the last year and a half. I drive home every weekend about 400 miles round trip. So over 90% of my milage is on the highway with the cruise set at about 77 mph (pretty much a straight, flat and boring drive). What would be your opinions of how often I should change my oil other than every 3500 miles. I have a 2010 LE with Tow Package but have not towed anything yet.