Not that it was a 'newer' vehicle, but I ran my 4.0L 2000 box Jeep Cherokee weekly on interstates for a while. The fuel economy on a non-stop 200 mile run was 23~24 at 55MPH and 19~21 at 70MPH. It stayed below 20 as I went over 70MPH. It had an instant / avera... Login to read more.