A Diesel Exhaust Fluid (DEF) that includes urea, demineralized water and between 5 and 300 ppm formaldehyde, acetaldehyde, propianaldehyde, or butyraldehyde, and this formulation of DEF include less than 0.6 ppm of phosphates, calcium, iron, aluminum, magnesium, sodium, and potassium, the formulation also includes less than 0.3 ppm copper, zinc, chromium, and nickel. This formulation of DEF reduces the accumulation of urea deposit in the diesel exhaust system relative to other formulation of specification grade DEF that include less formaldehyde.