Using &quot;limp mode&quot; with warnings to ensure the tank stays filled (and the car does not run at full throttle unless it is filled) is a much better solution.<p>When the sales guy told me the tank only had to be filled at service intervals, it sounded strange. People on the TDI forums thought it was just because VW didn&#x27;t want to scare away customers with an extra thing to do, but you can buy the stuff at any gas station and pouring it into the tank is not difficult.<p>When the scandal broke the assumption was that they mistuned the DEF cars out of arrogance, and again to avoid spooking customers with extra maintenance.<p>Now it sounds much more like they tuned it that way because this regulation would have crippled the car with an enormous DEF tank otherwise. It is possible that such a regulation combined with a 10,000 mile service interval only makes engineering sense on mid-size trucks or larger.<p>This doesn&#x27;t have anything to do with them failing to build a working LNT solution and cheating with those previously, of course.