DEF Math
The owner's manual says my truck has a 5.5 gal DEF tank. I waited until I was down to 1/4 on the gauge, just above the red zone, and added a 2.5 gal box of Blue DEF from Advance Auto. Now the gauge ...
Forum Discussion
Blue is $10 at Costco and that's what I've been buying lately because it's the most convenient. It's only a buck a gallon more than buying it at the pump.
