OTC Refractometer Kit for Diesel Exhaust Fluid (DEF) 15–40% Range — Portable DEF Tester, 0.5% Accuracy

The OTC 5025 Refractometer Kit is a handheld optical tester that quickly checks Diesel Exhaust Fluid (DEF) concentration to confirm the proper 32.5% urea solution for SCR systems.

Keep SCR-equipped diesel engines running within manufacturer and regulatory guidelines by verifying DEF strength on the spot. This compact refractometer uses light refraction across a prism and a magnified reticle to display concentration readings, letting drivers and technicians detect off-spec DEF before it affects emissions control systems.

How does the refractometer determine DEF concentration?

The instrument measures how much light bends when passing through a DEF sample on the prism. That bending corresponds to a position on the internal reticle, which is calibrated to show percentage concentration specifically for DEF solutions.

• Place a few drops of DEF on the prism using the supplied dropper
• Close the cover, hold the eyepiece to your eye and point toward light
• Read the concentration on the reticle scale, accurate to 0.5%

What readings and range should I expect from this kit?

The scale is marked with a clear waterline and covers a practical DEF range for fleet maintenance. The instrument is graduated in 0.5% increments and highlights the critical 32.5% target used by SCR systems.

• Indicated scale from 15% to 40%
• Graduations at 0.5% for precise checks
• Clear 32.5% reference marking for standard DEF

What comes in the OTC 5025 kit and how durable is it?

The kit includes everything needed to take immediate measurements and maintain the instrument in the field. Components are packaged in a protective case for transport and on-site use.

• Refractometer calibrated for DEF concentrations
• Plastic dropper, lens cloth, screwdriver and instructions
• Hard case for storage and safe transport

Why test DEF instead of assuming bottled or bulk fluid is correct?

DEF quality can degrade from contamination, dilution or improper storage, which may lead to off-spec urea concentrations. Periodic spot checks help avoid SCR malfunctions, costly diagnostics, or downtime attributable to incorrect DEF composition.

• Detects diluted or contaminated fluid before it enters the SCR system
• Simple process suitable for drivers or shop techs without lab equipment
• Quick verification at truck stops, depots, or fuel islands

Who this is for: The OTC 5025 Refractometer Kit is designed for fleet managers, diesel technicians, owner-operators and roadside personnel who need a fast, portable way to confirm DEF meets the 32.5% urea/water standard used by most modern heavy-duty SCR engines. If you service Detroit, Cummins, PACCAR, Volvo, Mack or similar diesel platforms and want a reliable field test to avoid emissions issues and unnecessary repairs, this kit provides a compact, accurate solution.