Bedlam wrote:
docdvm wrote:
I bought a 2017 Ram 2500 with the Cummins 6.7 Diesel. Previously had 2 Ford F150 ecoboost. I am getting better mpg from the Ram even though it is not yet broken in. The DEF fluid lasts a long time and has a gauge so you know when to pick up some more. I really like this truck but have not towed with it yet. Daily driver for now.
I find that DEF usage is based on the amount throttle you need apply to hold speed and how much temperature the engine is currently creating. If you're driving unload in cool weather on flats with a tail wind, DEF usage seems to be minimal. If you towing a heavy load on a hot day over steep grades or fighting a headwind, the system has much more thirst for that DEF to keep NOx emissions down.
While this is true, there is also one more thing that also effects DEF usage and that is the quality of the DEF itself. The system operates on an as needed basis to reduce NOx. Basically it will inject more and more until the NOx is at the desired levels. So if the quality of the DEF is low, then it will use more of it to bring down NOx to desired levels.
DEF does have a shelf life that gets shorter as the temperatures rise. The shelf life at 50F is about 36 months, 75F is about 18 months, 85F is about 12 months, and 95F is about 6 months. Past these time periods and the DEF quality will start to degrade requiring you to use more of it to lower NOx. This is why I always recommend to DEF from the pumps at a high volume truck stop that stores it underground rather than the jugs. That way you will know it is more fresh since it is stored at colder underground temps and is has not been sitting for a long period of time in some hot warehouse.