There has been lots of discussion on this topic over on sprinter-source.com. There seems to be 2 schools of thought, run it out and then fill or keep it topped off. There doesn't seem to be a clear winner.
I don't use much DEF in my 2015 Sprinter, approximately a 2.5 gal box per year. I also use a DEF refractometer to test mine. As long as it is good, I just add a box every 8K or so and keep going. I have yet to drain and fill, but will if it tests poorly.
__________________
Moderator
2017 Jay Feather 7 22BHM Baja/Andersen WD
2018 F150 4x4 3.5L Ecoboost Max Tow
2015 MB Sprinter 2500 Passenger 2.1L Diesel
2007 Ram 2500 4x4 Cummins 5.9L G56
|