I have acquired a 2011 T4r and want to know if anyowne has pulled a travel trailer with theirs that weighs over 7,000 lbs? Mine pulls the coleman pop-up that weighs around 3,800 ok, I got 15.4 miles per gallon on the 45 mile trip. I have the oppertunity to get an up grade but it is quite a bit heavier. Zi/