What is DEF/Urea and how long does one (1) tank last?

DEF is a non-toxic solution of purified water and Urea. Urea is a non-hazardous, natural compound which is produced from natural gas and commonly used in everyday products such as fertilizer.

DEF is used in low volume, approximately 2 gallons for every 100 gallons of diesel fuel. You should be able to travel about 4000 miles on one tank of DEF.