PinBoss

Found this while Googling about DEF consumption. We have a 2021 Silverado RST with the 3.0 and have been having similar experiences to what seems to be commonly described in this thread. I tow a lot, and while towing, it goes from full to empty within 500-750 miles depending on the load. It's not proportionate to fuel consumption. Last night I ran out of DEF (according to the gauge) and got to the 500 mile countdown prior to reduced 65 MPH speed limit. I decided to drive 250 miles through that countdown, to ensure I was bone dry for DEF. Happened to stop at a gas station that had DEF at the pump, and at 3.8 gallons it was overflowing... so either the capacity is not the 5.2 gallons advertised, or there was still over a gallon of DEF left during that countdown. I would find that strange since it literally says that you are OUT of DEF, not just low... but perhaps just addition precaution? I wondered why when I was at 1 bar and out, even trying to fit 1 x 2.5 gallon box of DEF in would result in overfilling. First diesel for us, so learning as we go. Have a diesel Tahoe on order too, wondering if I should switch to gasoline.