Stock, I was getting around 16 to 16.5 MPG combined city/highway. But I immediately installed a lift and larger tires and then deleted. I'm still getting 16-16.5 MPG deleted, but that is with a lift and 37 inch tires. Most owners seem to report about a 3 MPG increase after deleting. As pointed out, you need to consider the area you live in. I don't have to worry about inspections. Some people do, and just reinstall their DPF and NOX filters for inspection once a year. Another thing to consider is that the EPA cracked down on "race tuners" that enable you to delete emissions controls so the price of these tuners has shot up. If you decide deleting isn't for you, the 2013 up Cummins get a little better milage than the 2010-2012's with less emission's problems.