2015 Ram at 120,000 miles. I was having such a problem with my DEF and a leaking EGR and was out of warrenty so I eliminated all of it and did the mildest tune from PPEI. I have missed all the warrenty money and fixes, they were to late. But all my problems went a way and my mileage went up 2.5 MPG. If you do this, I would get the tune from GDE, they are a lot better to work with. Do remember you do not have to get a complete delete, you can do a little bit or a lot or not at all and just get the tune leaving the rest intact. Still the full delete and the Tune was the best thing that I did, hands down.