As to the mpg, I have never seen 20mpg in my life. 25 or better sounds cool, would not be a factor in buying a rig though
		
		
	 
I had a 2015 RAM Limited Ecodiesel.  I'd done quite a bit of research on the mpg and after I bought it learned about all the ED issues.  I talked to an awesome RAM investor and high performance diesel mechanic and he told me what to do with it for longevity. 
1- remove all the silencing "death foam" from on top of the motor, valve covers, and fuel pump.  all this stuff does is hold in heat on critical wiring and electronics. 
2- pull the EGR intake tube and see how bad the intake was coked up.  it was awful.  he told me the right things to say to the service manager at a local dealership, and to make a long story short, they replaced the intake and my injectors under warranty. 
3- sign up for the class action lawsuit and take the money and invest in a tune.  i was able to get the Green Diesel Engineering non-epa compliant tune before they put the clamps down.  it effectively turned off the EGR electronically.  i got mine with transmission tune also, and it improved the shift points and included engine braking as well. 
The engine tune added around 30-40 net horsepower and 40-60 ft. lbs of torque.  However, the greatest benefit was elimination of the EGR and all the soot those little motors pour into the intake.  With this combination, I averaged 27 mpg combined and over 30 mpg crusing the highway.  I got 23 when pulling my 17' Lund deep V and the engine braking and overall towing experience was awesome.  The tune woke that motor up big time and it would even spin the tires off the line if I needed to gun it.
When I hit 110k miles, I learned about a tone ring issue in the transmission that was sidelining guys around 115-120k miles without warning.  The part tat failed was about $20, but when it failed it would break apart and cause catastrophic damage in the tranny.  This issue affected a significant percentage of these trucks and repairs were upwards of $4-5k.  Add the risk of turbo line fires in the engine compartment and I decided to trade it for a '19 hemi. 
Given the increase in my monthly payment and overall driving experience with the hemi, in retrospect, I wish I would've fixed the tone ring and turbo line issues. in the '15  That truck was the total package with good power, excellent mpg, 4 corner air bag suspension, crew cab room, and plenty of off road capability.  Hindsight is always 20/20.  
