Question and Answer Forum

MISCO Refractometer Q&A Forum

Find answers to many common questions concerning applications, operation, calibration, and maintenance of refractometers:

Diesel Exhaust Fluid (2)

Do you know of a refractometer that measures the shelf-life of DEF? I’m not as concerned about our contamination as I am the risk. I’ve heard that comes from it sitting idle in a tank for too long.

A Diesel Exhaust Fluid (DEF) refractometer cannot tell you the quality or shelf-life of the DEF, it can only provide you a measure of urea concentration. However, a concentration measurement can tell you if the DEF is over or under concentrated, and may indicate tampering. The MISCO DEF201 and DEF202 digital handheld refractometers can measure the concentration of urea in DEF but this is a measure of concentration only.

Can you use a refractometer to measure DEF Quantity? Is it acceptable practice to add water to adjust over-concentrated samples?

The Palm Abbe digital refractometer (DEF201 or DEF202) can be used to very accurately measure urea concentration in DEF to +/-0.1%. DEF is a composition of ultra-pure urea and demineralized water. ISO standards call for DEF to be 32.5% (+/-0.8%). If your DEF is over-concentrated, due to evaporation, you can add demineralized water to return the measurement to 32.5%. However, you should NEVER add tap water or well water to a DEF. Doing so can cause irreparable damage to your SCR components.