Rislone 4784 Crystal Clean Diesel DEF & SCR Emission System Cleaner, 1-Pack

2017 6.6 Duramax kept throwing a DEF code. I think it was due to crystallization on my sensors. I poured this golden nugget into my system and the codes went away and have not returned. I buy Walmart DEF for reference. I’m about to pour my 2nd round in since it’s been about 6k miles since my last dose. Highly recommend.

My check engine light was on and I had a P2002 code. I added Rislone 4784 Crystal Clean Diesel DEF & SCR Emission System Cleaner and some fresh DEF. After driving about 200 miles, the code cleared itself. I think the issue was that my DEF had crystalized and needed to dissolved with this cleaner. Rislone also makes a DEF additive to prevent crystallization. (Rislone Diesel DEF Treatment) I'll be adding that to my DEF tank from now on.

As always, I'm skeptical when it comes to product performance—but this one? Amazing. I never owned a diesel until I bought my '21 GMC HD2500 Duramax. I love it, but man, diesel engines demand preventive maintenance. You can't wait for things to break—you’ve got to stay ahead of it with products that help reduce or even prevent issues. This particular product is excellent. Since the day I bought my truck, I’ve had nonstop problems with the DEF tank sensors sticking. Sometimes it would show full when I knew it wasn’t, and other times it claimed to be half empty right after a fresh fill-up. Totally unreliable. And what did the dealer say? “It’s inadvertent.” That word should be banned—it’s just an excuse to ignore a real problem. Let me tell you—this product works. Period. And it worked fast, too. Absolutely amazing.

It actually worked. Very happy with the results.

As a first time user of Rislone product, I’ve been pretty much satisfied with it. We’ve had our ‘015 F-350 series nice it was new and with nearly 200,000 miles, have noticed the residual left-over DEF crystals both in the containers & around the truck’s feed cap. Although never had any known symptoms from the DEF crystals (other than maybe when replacing the DEF heater & a couple exhaust sensors), this additive should rid the truck!s DEF system of those crystals.

Worth the try. I own a 2015 Volkswagen Golf sportwagen TDI. I would always have a check engine light with a P204F00 code for Reductant System Performance Bank 1. After taking it to the dealership and a bunch of replacement parts I still had the P204F00. At this point everything dealing with emissions was pretty much replaced. I saw this product and figured id try to clean the DEF fluid. I had about half a tank of DEF in the tank, poured half the bottle in and let it sit for 8hrs. Topped off DEF with new fluid. Took it for a hour and a half drive forcing it to regen. Got home and let it sit. Next morning the code and check engine light was gone. It’s been about 3000 miles since the cleaner was added and the codes haven’t came back. Well worth the try.

Seems to work. But how would you know until after some time.

I bought a used 2021 F250 with 75k miles. At first it was drinking DEF. I used 3/4 of a tank on a 900 mile road trip. I used this product on the first tank on my 5900 mile move to Alaska from Virginia. The first 3/4 tank of DEF, with the product in it, got me to Indianapolis, about 800 miles. The second tank I started using the Rislone DEF Treatment in every box I put in the truck, it got me to Mitchell, SD which was about 1000 miles and I used half a tank. About 1200 miles later I put 1 box of DEF in before I crossed into Canada, and stocked up on 3 boxes knowing I had about 3k more to go. Keep in mind, I'm hauling a 20ft enclosed trailer full of all my earthly possessions, and I have quite a few tools and heavy things. Something happened after that first 3k miles. I made it the next 3k miles and only used 1/2 tank. Now when I fill up it says 7500 miles to empty. I don't know if that's true, but it's been a long time since I've had to buy DEF.