I owned a 2016 ecod. I bought it with 60 k miles as the lower end of the motor went out on first owner. The motor they put back in was I am pretty sure a gen 3. I drove it over 2 years from 60k to 100 k. No problems. Could get 30 mpg at 60-65 no wind, Pulling a lightboat or trailer cross country 16-18. I liked it but as warranty wore off I got nervous and traded for a 2020 ram off road with a hemi. Problem with the hemi is it really like 89=91 octane and that cost 60 c per gallon more then the 87 in my town. So fuel cost per mile is deff more with the hemi. I do like it but my 3.6 v6 ram likes the 87 octane just fine and gets better mileage than my hemi. Not as fun to drive but have used it to pull the same trailer cross country and cost per mile is as low as the ecod without the emissions risks.
As was posted earlier all these engines are tuned pretty well and each gallon of fuel only makes so much power so just got to decide what engine. The low rpm torque of the diesel is pretty nice. If the lag in stop and go traffic doesnt bother you or you dont do much of that type of driving give it a shot I liked mine.