First of all, the DEF is a red herring. It's usage is very little.
Second, we have a 2012 Tour with a Cummins 450hp engine (heavy & tag), has never run "HOT" in the past two years. And we cross the Rocky Mountains (going & coming) 95% of the time. At various rallies I have asked other owners about the heat gauge not going over the middle mark and they say theirs doesn't do it either. So I believe the running hot, from my personal experience is a non-issue.
Our last 6 month trip, out west (mountains) we averaged 8.4 mpg over 5,800 miles as measured at the pump. Our 08 Tour 40', no tag, with a particulate filter did about the same after about 10,000 miles.
I do agree every time the EPA makes changes, the engines and owners suffer.
Kerry
