I honestly have NO idea how it calculates the DTE. I've never found it to be remotely close to accurate in over 6,600km. (4,100 miles) I'm normally doing 630-650km (just over 400 miles) on a tank for my commute with enough left in the tank that I could probably do at least another 100km/60 miles before DTE would actually hit zero ... and then I'd still have about 80km/50mi of 'reserve' in the tank. But even on a fresh tank, it normally never says more than about 520km on the DTE. It's ALWAYS very much lower than actual. But then again, so is my mpg on the dash. Consistently backed up by my Fuelly recordings. It's saying 8.8l/100km (27mpg) on Fuelly all-time, my dash says 9.3 (25mpg). It has consistently off by about 2mpg since day one. Not sure what the deal is, but it is consistent. Might be something to do with the speedometer being 1mph higher than actual. (GPS and radar speed sign verified.)