when i bought my 2016 Ram eco-diesel, i took my first long trip to Connecticut & back.
Remember this is the first eco-diesel in a Ram, i think they called it Gen 2
I got 27 MPG, i was almost singing.
Then they Flashed it, MPG dropped to the high teens
Then they figured out that they over did it & Flashed it again, the mileage climbed back up to 23 MPG Highway & that is what i am still getting.
I have never Hand Calculated it, so take that into account.
By the way, Stellantis is going to put the Eco-Diesel engine into the 2023 Maserati & a few other vehicles
So i had planned to but another eco-diesel Ram next year, & they won't be selling them.
I may be getting my current engine rebuilt when it gives up