@Fraidenburg - we may want to split this topic off into a new thread, as DEF usage isn't related to EGR although both systems are emissions-related but do two (2) different things.Just got the 20E04 for my 2018. It has just under 19k miles on it. My def tank gets less than 3500 miles when full. Is this normal or something more going on with the EGR?
It's definitely not in regen mode. the DPF will clean itself when towing thanks to the higher temperatures, and it likely won't go into regen unless you max out the distance of 350 miles, then it will automatically clean out whatever's in there even if not at 100% full. DEF injection rate is related almost 100% to exhaust temperature, as NOx forms under higher heat. So the higher the EGTs, the more DEF needs to be injected to counteract the increased NOx formation. This is a good thing, because otherwise you would need way more EGR to lower cylinder temperatures. DEF is the main reason that these trucks need about 25% of the EGR volume that older emission systems required (think 6.4, 6.0, etc). In fact, at high loads your EGR may be 100% closed for optimum power, and so the reduction of NOx relies solely on the DEF injection, i.e. more of it. So It's true when they say there's nothing wrong. Usage will be even higher if it's hot outside.My DEF usage is all over the place. I swear when I hook up a trailer it goes into permanent regen mode. It never quits and goes from 5000 miles on a tank to 1250 miles. Been this way ever since I bought it new. Stealership says there is nothing wrong. Pulling trailer from AZ to TX I filled the DEF twice.