So I've had my 18 platinum F150 diesel for about 5 months now. I filled it full of DEF when I first got it as the dealer did not and it was about empty according to the gauge, filled it up and took 4-4.5 gallons so gauge was reading correct. I have put on about 3-3500 miles since owning it doing some towing with it. My DEF level according to the gauge was showing between 1/4 and 1/2 and then I got a warning saying my def level was low and I had 400 miles to refill as I had just left on a fishing trip pulling my enclosed trailer 230 miles one way. I brought with a 2.5 gallon jug of DEF just in case but figured the dte calculation would change along the way, it did not. On the way home I got a message saying the def tank was empty and I had 100 miles to go until the speed would be limited to 50mph. My def gauge still showed above 1/4 tank, but the next town I pulled over and poured my 2.5 gallon jug in and truck was happy instantly. Def level jumped to 3/4 full and now the dte calculation was up to like 6000 miles. So the gauge was working correctly but I am wondering why it was telling me the tank was empty when it clearly was not. Anyone have any experience with def level and dte calculation being off?