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on May 17, 2014
As an ASE Certified tech myself, I never had any faith in anything that is dumped in the gas tank that claims it repairs catalytic converters (or anything else, for that matter). Understanding the fuel injection system as I do, as well as the ultra high combustion chamber temps and the incinerating heat of the converter itself, I knew nothing could survive such ungodly heat and molecular transformation to "clean out" the fuel system or the exhaust system, much less the catalytic converter itself!

But faced with a PO420 code myself and determining the problem was indeed my cat, I reasoned that a $25.00 investment was worth a shot.

I bought a bottle and dumped it in my tank at 1/4 full as the instructions say. I drove the 15 miles and then refueled. I reset my CEL and drove for over 100 miles with the light staying off. However, when I scanned it again, it still had a "pending" PO420 code even though light was off.

20 miles later, the light came on again so I was about to chalk Cataclean up as a big hoax. But upon reading more reviews, I found that some success stories stated that they acheived success only after buying a 2nd bottle and trying again. So I decided to give it a 2nd try.

This time I let the fuel tank go slightly below the suggested 1/4 tank and I poured the 2nd bottle in the tank. Instead of just a slow, normal 15-20 mile drive I went out on the Interstate and punched the throttle wide open to over 5k RPM for about a half mile. Then I slowed down and did it again, and yet again. All 3 times black exhaust streamed out the tail pipe. Then I just ran it steady at about 70 mph til the tank was almost empty.

I refueled with Sunoco 93 Octane because I thoiught it could only help the cause. I then reset the light, drove another 100 miles, and then did another scan. This time the "pending PO420" code was gone and the "codes" list was empty, stating "NO CODES".

I have driven over 1,000 miles since and still no light and no codes! So I can personally attest that Cataclean is an authentic winner! My advice to anyone is to drive it longer than 15-20 miles and don't be afraid to punch the throttle to "blow out" the carbon while the Cataclean is doing it's thing. It really did work for me doing it that way. Good luck to all!
77 comments| 208 people found this helpful. Was this review helpful to you?YesNoReport abuse
on February 26, 2011
I have an 02 Chevy Tahoe with 127K on it. I've been throwing P0420 & P0430 codes for about 8000 miles, and lately they come back within a day of being cleared. Following the advice of another reviewer, here's what worked for me:

I used CRC 05110 Mass Air Flow Sensor Cleaner - 11 Wt Oz. first to clean the MAF, let the car warm up for about 20 minutes, poured a bottle of Cataclean in the tank and drove for about 25 minutes (less than 1/4 tank of gas in the car). Then I cleared the error codes. Let the car sit while I was at work, drove it home, put a bottle of Lucas 10020 Upper Cylinder Lubrication & Injector Cleaner 5.25 oz. in the tank and filled up with Premium gas. I've driven for 70 miles and the code hasn't come back. I just passed inspection this morning.

I don't fool myself that this stuff will cover up a bad catalytic converter. But I can say that for me, whatever it did was good enough to allow the car's ECM to run the emissions test at least a couple of times without registering an error code. I don't care if the code comes back tomorrow. For the $35 that I spent for the three bottles, I have delayed a $2000 plus repair.
2727 comments| 137 people found this helpful. Was this review helpful to you?YesNoReport abuse
on October 16, 2011
Another reviewer said this is not a miracle product, but for me it was. It truly has saved me $975. My 2000 Chevy Prizm check engine light has been off and mostly on, for like 10 months. It was time for inspection and I didn't pass because the light was on so I took it to a dealer (yes, I know, I know but the last time I didn't go to the dealer when the check engine light was on it went in the shop 5 times and was never fixed correctly until I took it to a dealer). On top of a whole host of other completely inflated and bogus repairs they suggested, they told me I had to REPLACE the catalytic converter to the tune of $1,000+. There was no other option. This was it. For an old, high mileage car it wasn't worth it and I came very close to just selling the car to a junkyard.

I have my own code reader Autel MaxiScan MS300 CAN OBD-II Scan Tool which I bought for $20. The dealer charged $60 to tell me the same code as this reader gave. The code was P0420 which is catalytic converter insufficiency.

I used the Cataclean exactly according to the directions on the bottle and right after pouring it in the gas tank, I reset my code reader. The check engine light came on 9 miles later. I thought maybe the Cataclean had not had time to work so I reset it again. It came on in 25 miles. I thought, it's getting better. I reset the code reader one last time, drove 50 miles with no problem, got my car reinspected and PASSED! I have now driven more than 100 miles and still no check engine light. I will recommend this product to everybody, all the time - and I mean all the time. Like you'll say, hmm, I wonder what I should have for lunch today, and I'll be like, hey did I tell you how great this Cataclean product is that I bought from Amazon? And you'll be like, yeah, about a 100 times.
77 comments| 98 people found this helpful. Was this review helpful to you?YesNoReport abuse
on July 25, 2014
07/25/2014 - About two weeks ago my 2005 Honda Civic's computer threw a code and the engine light came on. I plugged in my ODBII reader to get the code(s) and got a P0420 Catalyst System Efficiency Below Threshold. Generally a mechanic will tell you that you need to replace the catalytic converter... about a $1,000+ job in a civic. I reset the computer and the engine light went out.

Given what the catalytic converter's job is, it stands to reason that it can get dirty and the screens clogged with carbon deposits. The same with the O2 sensors. Did some research on the web at found this product. The reviews were mostly good. In the meantime the engine light stayed off for a week. Once it came back on, I put a good fuel injector cleaner in it as I just had an oil change and I usually put fuel injector cleaner in at the same time. I reset the computer with my OBDII reader, and ordered Mr. Gasket Cataclean. Four days later the engine light came back on.

The cataclean product came and I waited and drove until I was below a 1/4 tank of gas so I'd run the max strength of the product through the fuel system. Put it in an drove mostly highway miles at 60 mph or better for 75-80 miles over two days. Last night on the way home from work the low gas light came on, so I pulled in to fill up and turned the car off. When I started the car after fill up the engine light went off on its own. So it looks like the product did the job.

Immediate results: Big difference in acceleration a whole lot more pep. Engine is quieter. Idle RPM's have dropped. The engine and fuel system have that little growl again like the car is breathing much better. I now assume that gas mileage will improve.

My car is not due for inspection for another year. If this product proves out over time. I'll put it in every 12,000 miles just for better performance and mileage. I'm at 122,875 on the odometer. I will update this review over the coming months as to whether the the engine light comes on again.

08-01-2014 - Engine light came back on with the catalytic converter code P0420, mileage 123,312. Car is still running better than before the treatment, and would have passed inspection. I will probably try another bottle in week or so and report back.
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on September 25, 2014
Long story, short it worked!!! and passed the state inspection

Long story -- -Wife's car - 2006 Hyundai Sonata with a P0420 bank1 code.(check engine light) This is the catalytic converter and O2 sensor between the engine and the firewall (very tight and hard to get to) -The repair itself would have been over $400 bucks just for the parts - as the catalytic converter is connected to the exhaust manifold, and the O2 sensor is about another 100 bucks - - so that would be my expense and me doing the labor. If I took it to the dealer they wanted between 800 and 1000. So I had a decision to make.

I ordered three different products from Amazon. 1) Mr. Gasket Cataclean Fuel and Exhause cleaner. 2) CRC Mass air flow Sensor cleaner, and 3) Lucus fuel treatment - All three products came to 47 bucks- -

The job follows - - I disconnected the negative battery. By doing this, and leaving it disconnected for about 15 minutes, this cleared the check engine light. Next I cleaned the mass air flow sensor as directed on product label. this was pretty easy - just un-clipped the sensor wiring and sprayed the connectors. Next, I poured the Cataclean into the gas tank (note: open the gas filler cap before you disconnect the battery - as it has an electronic opener and will not work if the batter is disconnected) there was a bit less than 1/4 of a tank of fuel.

I told my wife to drive the car the required 50 miles (for a NC safety and emissions check they require the vehicle to be driven 50 miles after the check engine light has been cleared) -(actually told her to drive it like she stole it - hard and fast) then have the yearly exhaust and safety inspection done.

Prior to the inspection she needed fuel - so I told her to fill up with premium and add the Lucas fuel treatment to the tank.

Here's my guess on WHY this product (Mr. Gasket Cataclean) works - the P 0420 code is a inefficient catalytic converter - meaning that the catalytic converter is still working just not as efficient as government requires (they require 95% and above) - so it could have been working at 94% or less. Cataclean breaks down the carbon build up (somewhat of a solid) inside the catalytic converter and turns it into a gas which passes out the exhaust system.

If your catalytic converter is completely dead, or the O2 sensor is completely bad, none of these products will work - - but....... if everything is still working and just "dirty" then this process should help clean off the build up. Read your check engine light code - and break it down - understand the different "banks" (all V-6 and V-8 engines have two banks (1 and 2)) Bank 1 referrers to the sensor and converter associated with the # 1 firing piston, therefore bank 2 would be the other side of the engine

UPDATE 11/20/2015
well that process worked and enabled me to pass the emissions test back in OCT 2014 - the light stayed off for some 3K miles - but then came back on - - at which time I simply disconnected the battery for a few moments to "reset" the OBC - - after that the light would staff off for some 500 - 700 miles

When it came time for the emissions test for 2015 - I did the same process again - - passed the NC emissions test and didn't look back

Honestly.... I feel this product does clean the catalytic converter - - so until my care completely dies - I"m guessing I'll do this every year
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on August 21, 2014
Ok, here we go. This is a good product, as long as your catalytic converter is intact and not crumbling. It is strictly a temporary cleaning for emissions inspections (like in California). I dropped it the tank, as instructed, with about a quarter tank of fuel still in there. I drove it for about 10 miles and added more fuel. I had previously cleared out the catalytic converter efficiency DTC. I drove the car for about 30 miles on the freeway to allow all the monitors to run. After that distance, I checked the monitors with a handheld DTC scanner. It indicated the catalytic converter and the other monitors had run successfully and everything was operating properly. I drove straight to the smog inspection station and about 20 minutes later, the car passed California emissions. According to the smog technician, the different levels were low except for one. This particular emission, don't remember which one, is indicative of a catalytic converter that is in a deteriorating stage. Sure enough, I drove the car one more day before the "Check Engine" light came on. I used the scanner again. It came back with the same catalytic efficiency DTC. So to recap, it is strictly for temporary cleaning of a catalytic converter that is physically intact but not performing to the required standard. If you have a crumbling, rattling catalytic converter, this or any other cleaning product will not work. Use at your discretion, you know the condition of your vehicle better than I do. I would recommend this to anyone, as long as you have realistic expectations, follow instructions and fully understand it is temporary.
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on March 23, 2013
I haven't had an emissions test since I used this product, so can't say if it improved in that area. It certainly did improve performance in several areas. The car starts much easier, idles smoother, throttle response is better, has more power, and runs smoother. My mileage has improved. but not by a great amount. While I am not a believer in the chemical solution to mechanical problems (dirty O2 sensors and catalytic converter), this seems to work to eliminate the problems associated with older vehicles and the use of ethanol enhanced fuel.
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on September 22, 2013
I have been getting an intermittent P0420 OBD2 code and had the sulfer rotted egg smell typical of a catylitic converter on its way out. I have used other fuel system cleaners with no luck. I used one of these after hearing positive reviews from a friend who is an auto tech. Ran it for 40 miles and then filled the tank with premium and turned off the engine light using my scan tool. That was almost 600 miles ago and the P0420 code hasnt returned. (code used to come back every 30-40 miles) Plan to just use this stuff every few months instead of replace my cat. (saves about $1600) There is no magic cure for a bad cat and I'm sure it will be an issue again some day, but this got me through another year of emissions inspections without spending alot of money on repairs. I am very happy with the outcome.
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on March 18, 2016
First off let me say I am always skeptical about online reviews because I don't know who got paid to say what. But I am your average American Joe (Gary) who is an Evangelist, and I will not lie, too afraid of God. I have a 2005 Hyundai Santa Fe with over 329,000 original miles, original motor, original transmission. This is the first year that it did not pass inspection on the first try. I had two things off line (sorry don't know the technical terms) and in NC, for a 2005, you can only have 1. One was a heated O2 Sensor and one was low efficiency. It has had low efficiency for over 120,000+ miles, and I always used Lucas or Seafoam and it cleared the code and check engine light went off long enough to get in inspected. The light would soon come back on, but I didn't care as it was inspected. This is my primary vehicle. This year the Lucas and/or Seafoam didn't work as far as getting the engine light off. I researched many things, including Scott Kilmer saying put a gallon on licquer thinner in it. Well that didn't even sound reasonable to me so I didn't. Then I remember CATACLEAN which an auto parts store clerk told me to try 2 years ago. It was $25 a bottle so I didn't. Well, this year I said what the heck. I bought it and followed the specs, put it in with approx. 5 gallons/1/4 tank, drive 10-15 miles (I drove 15.2), and fill it back up (I purposely filled it up with premium). Light was still on that day. The next day I drove to work, 3 miles, and lunch, 10 miles, and when I got out of the place for lunch, the check engine light was off. I drove straight to the inspection place which was actually about 30 miles from where I was, and it passed inspection. I can't say what did or didn't happen to others, but for me, it worked. I needed my vehicle inspected to get my tags renewed. As long as my Santa Fe is running, and it stills runs great, I will use a bottle of CATACLEAN quarterly. I don't know what it did and don't care, I just know I am driving legal. As of this writing it has been 3 days and the engine light remains off. Good luck on your issues.
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on June 11, 2015
I had my check engine light on for weeks. I tried other products which failed to clear the code. I purchased and used this product one week prior to getting my car inspected and not only did it clear my code, it also passed inspection. It's been two months and no more check engine light and I find my car runs smoother.
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