Rislone 4720 Cat Complete Fuel, Exhaust and Emissions System Cleaner,16.9 oz. | Cleans Catalytic Converter, Reduces Emissions & Saves Gas

Kept resetting P0420 CEL on my 2007 Toyota Corolla, hoping I could quickly go through drive cycle and pass my smog check before it came back on. Same code kept coming back on within 2-3 miles of a reset so using Rislone was my last hope before I tried the non fouler trick. Below is exactly what I did, hope it helps someone! 1) Filled my gas tank with premium gas, drove it down to half tank over a few days of driving before I inserted Rislone. 2) Drove ~30 miles and then refueled to full tank with premium gas again(Half highway/half city as instructions state) 3) Instructions say after completing step 2, drive the car to 1/4 gas tank at which point CEL should clear. For me, I drove ~25-30 miles over 3 days, clearing the CEL each time it came back on. During the 3rd day (~60 miles since using Rislone), the CEL didn’t come back on and all monitors reset! Immediately went to smog station and passed. CEL is still off, not sure it will last but who cares! Car is running fine and I don’t need to pay for a new converter just to pass a smog test! Tips: 1) Not sure if premium gas made a difference but I read several people say they used non ethanol/premium gas which cleared P0420 so figured it couldn’t hurt. 2) I bought a cheap OB2 monitor which I kept on when driving so I could see exactly when CEL was coming back on and when monitors are smog ready. If you’re lucky, resetting CEL and going thru drive cycle may be enough to get past smog without using Rislone. In my case, the P0420 CEL would come on within 2-3 miles each time I reset the CEL so using Rislone was a must. 3) Each car is different but generally speaking, once you reset CEL the drive cycle consists of warming up the car for a few minutes and driving 50-60 mph a few times, ideally letting the car come to a stop with no or minimal use of the brake. Make sure A/C is off. Using the OB2 monitor while driving the car will help you get a feel for your cars drive cycle. 4) If a CEL code is pending, the relative monitor to your code will not clear! In California, all monitors except EVAP have to be ready to pass smog, your state may be different.

Not much else to say, there. I followed the directions to the letter (driving more highway AND city than what's instructed) and P0420 remains on the OBD. I've been told now by two very experienced mechanics that these products rarely work - after now trying both Cataclean and this one, I now understand why they say this. EDIT EDIT EDIT!!! Just changed to 5-star because, although it took driving the car beyond what the instructions say, it has worked perfectly. P0420 is now gone, vehicle passed state inspection "with flying colors" and registration is complete. Key take-away: Give this more time to work if it doesn't do the job right away. I did nothing different - same gas as always (I fill up with Chevron or Texaco almost every time as they include Techron in their gas and my former racecar driver brother-in-law says that's the best). I do also add a bottle of Techron on occasion to give an extra "boost" to the cleaning power.

Works great

It seems to be working but you never know. Value for the money. Easy to use, just pour into the tank

This product is not working at all it damaged & clogged radiator I advise do not use it

I have had an issue with my Bank 2 down stream 02 sensor for a year. It continuously told me the voltage was low on that 02 sensor. I replaced the aensor several times and it would be ok for a month, then I’d get the check engine light and the code using my OBDII. I had changed all four catalytic converters, checked for leaks, checked wiring, you name it. So. I decided to give this a try. Following the directions, and within 20 miles of driving, all of the codes cleared and my truck runs as it did when I bought it new in 2008. I got the 4 pack to continue maintenance and to use it in my wife’s car as well. I would not hesitate to recommend this to anyone as it will work to clean the entire fuel system immediately. Best product I have ever used over the last 50 years when I bought my first car at age 15.

Used it per directions. Light went off for a tank or 2 and then came back on. Easier to pour in the tank than to try and replace cats. It may work in some situations but in mine it was short lived.

2011 gmc acadia and have been fighting a P0420 Low efficiency bank 1 code for about a year or so. I've tried cataclean with inconclusive results only because I've done other things at the same time and code has cleared. Oddly enough changing the oil usually cleared the code but eventually came back. I've taken intake apart and, anyone who's owned an acadia, knows the poor fuel system design in the fact that oil gets into the intake and pools up. Along with changing PCV valves and modifying them, I've got the code to go away multiple times but this time, was not going away. I did the oil, cleaned intake, changed air filter etc., etc. Stumbled on to Rislone and it has some pretty positive reviews. I'm a believer in fuel additives and fuel system cleaners but I'm a little skeptical on stuff like this. As stated, I've used Cataclean before and other Cat cleaners with no luck. So, outta desperation, I got myself a bottle and followed directions....Dumped full bottle in when tank was 1/2 full. Drove to my destination about 25 minutes away, mostly highway/high speed roads. It was a 16 mile drive, check engine light was still on when I shut the car off. Did what I had to do, started car 10 minutes later and low and behold light was off!! I couldn't believe it. Drove another 10 miles or so, filled up per the directions and drove home. If I think about I'll update this post down the road but I'm impressed!! UPDATE - CEL came on again after 8 days. Do it works but then doesn't??? I dunno.

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I had an engine light come on in my 3010 Honda Accord. OBD2 scanner said it was a catalytic converter issue. I put this into my gas tank when it was about half full. After a few days of driving, it fixed it and the light is off. I've done this once a year for 2 years and it keeps working. Love it as a cheap way to prolong the life of your old car!

Best !! Engine light is gone now. It’s a been a week and I am not seeing the Engine light anymore 😊

Does not work for me, and no guarantee as the described

I said I would write a follow up. Put in around Christmas see review. Have now put about three tanks of gas through pickup truck. No codes have come up since. So would say it well worth buying. I had all sorts sorts of codes showing up turning on eng light had to clear every 1/2 tank.