talking about the Cummins diesel in the Dodge , I replaced my 2006 Ford 350 Superduty with an 11ft utility body which was getting 8 miles per gallon ( it was getting 11 mpg new and loaded light ) , I got a Dodge 4500 with a 6.7 turbo Cummins with 14 foot of utility bed and it is loaded down , the highest I have achieved on the highway and keeping my foot out of it is 15.8 , I cut my fuel bill in half , I travel a lot and was burning on average $80 per day with the Ford , thats $400 a week ( 5 days ) as I never work on the weekends , I figure I am saving $200 a week on fuel , 52 weeks in the year is $10,400 , the Ford was paid out and my note is $600 for the Dodge , so I make $200 a week driving the Dodge figuring I save $800 a month on fuel , the 4500 Dodge has a 52 gallon tank with $4 per gallon diesel when I run it down to the low fuel light it takes $200 to fill it up which is ludicris , the fuel filter on that engine is $50 and it is a very different hy tech looking filter ----------another thing is oil changes , the Dodge owners manuel says if you use sythetic oil you can go 15, 000 miles on a oil change , which I don't , I am going 10,000 , the Ford was 5,000 ---------- so if you can cut your fuel bill substainsaly it doesn't take long to recoup the investment