OTC 5025 Diesel Exhaust Fluid (DEF) Refractometer Kit - Includes Refractometer, Dropper, Lens Wipe Cloth, Instructions and Quick Start Guide, Screwdriver, and Case

Easy to use and read display. Accuracy unknown for lack of a known calibration fluid other than water, but new package of Blue DEF checked good.

Just bought a new 2023 semi truck $220k didn’t even have 3k miles when a check engine light with poor def truck derated shop said def was contaminated. I got a bill of $1900. I sent bill to seller he paid the bill contamination is not cover under warranty somebody had to pay that bill truck got fixed bought this tool every jug I put in I test well 3k miles again check engine light poor def again I told shop I checked every jug bought def fluid from there parts counter well shop gave me a bill for $6,200 i checked fluid and showed my refractometerwell they started doing there job come to find out the builder of the truck for some reason caked on a bunch of grease on O-ring that goes on sensor that was leaking into the tank and creating false readings and that’s where the contamination was coming from. I suggest if you have a semi truck that uses DEF buy this tool it’s worth every penny. By the way, the $6200 bill got covered under warranty.

So easy to use, the pamphlet instruction is included, it cost less than you order directly from OTC. The glass screen show your DEF testing fluids very clearly and 99% accuracy, works as it design for.

This DEF optical test device works perfectly and is quite accurate. My only complaint about OTC's claim of "optical grade quality" isn't quite true. My unit came with a quite noticeable black spot located a little above the distilled water calibration line. That's not optical grade in my experience!

I’m pleased with the quality. It’s easy to read and use. Judging by the quality appearance, I’m going to believe it’s accurate. You are able to calibrate before each use. With DEF mfg now removing their “secret” date codes all together, you need something to verify the concentration of what you’re putting in the tank.

I drive a 2014 Ram 3500 that uses DEF. Got an alarm the other day and upon determination the code said problem with DEF conductivity(weak DEF in tank). Service writer said I used cheap DEF (I didn't) and for a mere $1200.00 they would drain,flush,and re-fill tank with the "good" mopar DEF.Told him he was full of poop and to clear the fault code. Used my new OTC refractometer to check DEF in tank and it was fine. Now dealership will DO THEIR JOB and trace stray voltage/fault in DEF monitoring system. I got to wonder how many unsuspecting diesel truck owners whose engines require DEF fall for the $1200.00 drain and flush scam. Disgusting.

Works as advertised. I like the idea of checking the fluid; perhaps a bit OCD, but worth the peace of mind.

I use this every time I get DEF. Only once have I bought bad DEF, which this detected. Without the tester I might have put bad DEF in my truck. Prior to getting this refractometer, I had a specific gravity DEF tester. It was much less expensive but it was hard to tell what the reading was half the time; it was not consistent. The refractometer is much better and only takes a minute.