2015 Silverado 2500HD High Country Duramax 6.6L. The DIC for DEF reads 30% and I added 2.5 gallons a few days ago. Temperature has been below 20ºF to -12ºF for several days. Today got up to 25ºF. I assumed the DEF froze and hoped it would thaw with heaters, especially now with warmer temps, but it has not. I'm supposed to start a trip to Arizona from Twin Cities, MN tomorrow towing about 6,000 pounds. Is this too much risk, hoping the DEF sensors will thaw and I'll be OK?