Just got the dreaded Low Quality DEF light last night, and I've got an 800 mile round trip scheduled tomorrow that I can't miss. I've had it once before, and the light cleared itself on the freeway. I've driven 50 miles with the light on, even downshifting to get the RPMs high to burn off whatever crud is on the sensors (as instructed by many other related posts), but it's still on. What are my options at this point? My only thoughts are to take off as planned tomorrow, and hope that some serious freeway time will fix it (I live on an Army base, so the car rarely sees the freeway ), or if it doesn't fix itself like it has in the past, drop it off at a dealership on the way there and pray they give me a loaner so I can keep rolling.