This sucks and now getting worried. I'm in the military, got deployed for 4 months ended up turning into 7 months by the time I get back in May since October 2020. I have no one that can get to my truck which is a 2020 Limited EcoDiesel and start it. So since October 2020 my truck has been sitting dormant. I can not remember how much diesel I have in the tank but I do know the DEF is full. How long can diesel and DEF sit for? Now this isn't my first time doing this. I had a 2013 Ram 2500 and it sat for 4 months and it started like nothing happen and worked just fine. Of course I took it in to get the oil change and all that after. But this time it's different. Plus it is also not a Cummins. This is my 7th deployment but this one turned into the longest so I never had this issue with diesel.