I just got back from a weekend in Oklahoma City. I drove my rig from Asheville NC to OKC on thursday and returned monday morn 0400. Over 2000 miles in 4 days. My but only got sore if I pushed the rig over 75mph for any length of time. Best cruising was at 65 to 70mph. Best gas milage too. Going to run up to New Jersey in October.