When I traded my 2005 RAM diesel for my current 2014, I read that the factory fill had changed to 5-40 synthetic. I had always used 15-40 conventional in the 2005. I contacted RAM to ask why they changed and if I could still use the 15-40 conventional in my 2014. They told me that the recommendation had not changed: 15-40 conventional or 5-40 synthetic, depending on the temps in my area. The factory fill changed because they were selling a lot of diesel RAMs to folks in the north that really needed to use synthetic. He said that in my area (TN), I shouldn't be concerned about whether or not to used synthetic.I would also stay with recommended rating from the manufacturer. These new engines have really tight tolerances, heavier oil might cause a ticking time bomb issue.
If your 2014 is an ecodiesel, your deater is incorrect.When I traded my 2005 RAM diesel for my current 2014, I read that the factory fill had changed to 5-40 synthetic. I had always used 15-40 conventional in the 2005. I contacted RAM to ask why they changed and if I could still use the 15-40 conventional in my 2014. They told me that the recommendation had not changed: 15-40 conventional or 5-40 synthetic, depending on the temps in my area. The factory fill changed because they were selling a lot of diesel RAMs to folks in the north that really needed to use synthetic. He said that in my area (TN), I shouldn't be concerned about whether or not to used synthetic.