The 6.4 is problamatic. I had an 2008 for 3 years. It performed well but theres way to many potential issues with this engine, I changed over to a 6.2 2011 gasser. Much happier, the gasser is cheaper to run overall. The 6.4 was not economical at all. Aside from the big maintainance costs compared to the gasser, the 6.4 on its best day got 12.5 mpg on the highway withh the TC on. The 6.2 gas gets 10.5 to 11 mpg hauling the same camper. Factor in 45 cents more per gallon for diesel , the numbers do the talking.