As a car owner, you probably never thought you would find yourself searching on the internet for the best catalytic converter cleaner. 

That’s until you encounter the dreaded ‘Cat code (P0420)’, or the ‘check engine’ light starts to flash one fine day in all its glory. 

A more intrinsic diagnosis with an OBD II diagnostic connector will reveal the Cat or the Catalytic converter as the culprit. 

That tiny component of your vehicle that toils away in the underbelly, hidden from public view. 

The conundrum though, is how does one clean or fix the cat? 

There’s so much conflicting information out there.

There are YouTube videos that claim that dunking the catalytic converter in cleansing solutions should strip it clean of any silicate or alkaline deposits, and hence fix the code error. 

There are theories that soaking it in acetone is the easiest hack to fix any and all problems with the cat. 

The fact is that none of these are foolproof methods and might in fact do more damage than good.

A few might work as temporary fixes. But sooner or later, the code will reappear. 

If you have an emissions test staring at you, you might not have enough time to try out random stuff that you read on the internet. 

The best catalytic converter cleaners, like the ones that we’ve selected in this list, will get the job done without any elbow grease. 

If you are facing either one of these situations, then this article might save you tons of hassles and a $1000-2000 repair bill. 

Best Overall Catalytic Converter Cleaner – Cataclean

Last update on 2021-09-10 / Affiliate links / Images from Amazon Product Advertising API

Cataclean is hands down the most popular catalytic converter cleaner brand in the United States. 

It is a complete fuel and exhaust system cleaner that removes stubborn carbon deposits in the catalytic cleaner, the fuel injector, oxygen sensors and the cylinder head.

The result is a more environment-friendly and fuel efficient automobile with up to 50% reduced hydrocarbon emissions. Most importantly, no more Catalytic converter error codes. 

Cataclean is an EPA approved formula that’s legal in all states in USA. This means that you are not jerry rigging or using aftermarket components with dubious legal status. 

The most important reason though, why Cataclean is the best catalytic converter cleaner, is how easy it is to use.

Unlike manual cleansing methods in which the entire cat has to be removed, you just have to pour Cataclean into your gas tank and drive a few miles. 

It does not alter the fuel composition and there are different formulas for gas, diesel and hybrid engines. 

One of the common questions that we get asked, is how does this work. 

Cataclean works in two ways. There are some components in it that begin to dissolve stubborn deposits on the cleaner before combustion begins. There’s another bunch of components (mostly hydrocarbons) which improve the fuel combustion process. 

While it works to fix errors and clear emission tests, Cataclean is best used as a preventive measure before your catalytic cleaner conks off from excessive wear and tear. 

Best features

• Most popular catalytic cleaner brand
• EPA approved formula that’s legal in all 50 states
• Works to strip stubborn carbon deposits on the honeycomb structure 
• Cleans the entire fuel and exhaust system
• Super easy to use. Just add it to the fuel tank
• Proven formula that clears error codes

Best Choice for Fixing Bad Odor – Solder-It

Last update on 2021-09-10 / Affiliate links / Images from Amazon Product Advertising API

Solder-It is an easy fix for multiple problems related to the fuel and exhaust system. 

It can help you clear the catalytic converter code, if it’s flashing on the dash and preventing you from using all the features in your car. 

More importantly, it can help fix the ‘Rotten egg’ odor that emanates from the exhaust, and at times, can also leak into the cabin. 

This typically occurs when the catalytic converter stops converting hydrogen sulfide into Sulphur dioxide. In other words, the cat is either worn out prematurely, or needs to be cleaned to remove any stubborn deposits that might be affecting its performance. 

Just add Solder-It to the gas on a full tank and drive the car until the tank is ½ empty. Stop the car, clear the code and restart.

Bingo! No code. No odor either. 

Considering that the average repair or replacement cost for a cat can run into hundreds, Solder-It is a very cost-effective solution. 

While the brand does not explicitly claim that it can help you pass an emissions test, there are hundreds of customer reviews that claim exactly this. It has helped a wide range of automobiles pass the test with flying colors. 

Take that however you want. 

It is recommended that you use Solder-It once every five to six months to keep the catalytic converter working in prime condition. 

Best features

• Gas additive catalytic converter cleaner
• Helps clear common catalytic converter codes
• Helps eliminate the offensive rotten egg odor 
• Removes carbon deposits on the catalytic converter
• Keeps your fuel & exhaust system more efficient

Budge Option Cleaner – Hi-Gear Cat Cleaner

Last update on 2021-09-10 / Affiliate links / Images from Amazon Product Advertising API

The Hi-Gear Gas additive cat cleaner is a budget priced solution to some of the most persistent problems with a vehicle’s catalytic converter and the fuel system. 

If your car’s fuel efficiency has diminished, if it is hard to start, if the acceleration has reduced and the car rough idles, then all these might be problems with the catalytic converter, or one of the components of the fuel system. 

Hi-Gear is a very effective cleaner that completely cleans the combustion chamber, the oxygen sensor, the injectors, pistons and EGR valves. 

It can help you pass an emission test, eliminate the rotten egg odor, and reduce the emissions of toxic gases. 

One 16 oz. can suffices to treat 15-20 gallons of gas and should completely clean a catalytic converter that’s not overly clogged. However, if you have never cleaned the cat, then it might take a couple of treatments to fully clear stubborn deposits. 

It is priced way lesser than the more popular brands in this list. But according to the overall positive customer reviews, it is equally effective at cleaning a clogged cat as some of the bigger brands are. 

Hi-Gear Cat cleaner can only be used with gasoline engines though. You cannot use this with Diesel engines, which is a minor letdown. 

But if you have a gas engine and you aren’t looking to spend a bomb on pricier brands, give this a shot. We are sure that you won’t be disappointed. 

Best features

• Budget-priced additive cleaner
• Completely cleans the fuel and exhaust system
• Clears common Catalytic cleaner related errors
• One can suffices for common problems
• Removes rotten egg ododr
• Helps clear emission test

Award Winning Brand – Liqui Moly 8931

Last update on 2021-09-10 / Affiliate links / Images from Amazon Product Advertising API

Liqui Moly is an award-winning German brand that manufactures an extensive range of automobile additives for petrol and diesel engines. 

This is the 8931 catalytic system cleaner that contains a special blend of additives that break down even the stubbornest carbon deposits in the catalytic converter. 

It also flushes out impurities and removes sediments that clog the entire system and may trigger codes in your dash. 

Along with helping clear the codes and potentially helping you pass an emission test, Liqui Moly can also help improve fuel efficiency, reduce emissions and eliminate toxic odors.

Timely and periodic use of the cleaner helps maintain your cat system in optimum working condition, preventing expensive repairs and prolonging the lifespan of your vehicle. 

However, the application process may be slightly cumbersome, especially when you compare it with gas additives. 

You need to empty the contents of the can into a pressure sprayer (like the ones you use to spray pesticides), gain access to the intake tract that’s normally behind the turbocharger (may vary depending on your vehicle) and then spray it directly into it. 

The engine must be started before you spray it and maintained at a constant speed of 2-3K RPM. 

It’s not a big deal for someone who has prior expertise and some amount of mechanical skills. But for a newbie, it may be a little tough.

That said, customer reviews mention that Liqui Moly is one of the most efficient cat cleaners in the business. 

Best features

• Award winning German brand
• Special blend of additives
• Flushes out impurities and removes sediments
• Can help pass an emission test
• Helps clear Cat errors and the check engine light

OXICAT – Oxygen Sensor & Catalytic Converter Cleaner

Last update on 2021-09-10 / Affiliate links / Images from Amazon Product Advertising API

Oxicat is another German-made additive cleaner for the oxygen sensor and catalytic converter.

It is renowned for its decarbonizing formulation that not only clears sediment build up on the cat converter, it also helps dissolve soot and carbon deposits in the entire exhaust system.

Unlike Liqui Moly, that needs to be added to the intake tract, Oxicat can be added directly to the fuel tank, which is always the easier way to use these products. 

One 250 ml bottle can be added to 12-15 gallons of fuel, which makes it a very economical choice. Moreover, most customer reviews mention that a single treatment was enough to rid the car of the Cat error. 

It’s in very rare instances, that a second treatment was necessary.

Even if it does take two treatments, that’s way cheaper than spending $1000-2000 in replacements, isn’t it?

Also, Oxicat is compatible with petrol (gasoline), diesel and even hybrid-fuel engines. 

Using it periodically will help prevent niggling cat errors and improve the fuel efficiency and emissions of your vehicle. 

If your car is throwing cat codes at you that refuse to stay cleared, this should be an easy and cost effective fix to it.

Best features

• German made additive cleaner
• Powerful decarbonizing formula
• Cleans the Cat converter and the O2 Sensor
• Compatible with petrol, diesel and hybrid-fuel engines
• Helps eliminate cat error codes
• Improves fuel efficiency and emissions

Best for Older Cars – Motor Power Care

Last update on 2021-09-10 / Affiliate links / Images from Amazon Product Advertising API

This Catalytic converter kit from Motor Power Care is a terrific choice for older vehicles with severely clogged converters, or ones with On-board diagnostic ports. 

It’s a two-product kit that contains a foam cleaner and an additive cleaner for the cat, that provides a more intensive clean than some of the other products in this list. 

Using it is pretty simple. 

Both cans come with elongated nozzles that make it easier to spray and pour into the respective inlets. The foam cleaner has a white tube-styled elongated nozzle that makes it very easy to spray it directly on to the catalytic converter. 

The gas additive has a red nozzle, that makes it super easy to pour it into the fuel tank. 

So you open the upper port for the O2 sensor, spray it on to the Cat converter, add the additive to the fuel tank, rev the engine to get the temperature up (very important) and that’s it. 

Take the car for a drive and any errors or check engine lights should be fixed. 

It is estimated that this kit saves more than 70% of the cats that are throwing error codes or fail an emission test. That’s a great success rate. 

The only thing that you’ve got to ensure before application is that the cat converter has not cracked or melted. 

Best features

• Two-part kit for an intensive cleaning
• One foam spray to be applied directly on the converter
• One gas additive to be added to the tank
• Has a 70% + success rate in fixing cat errors and clearing emission tests
• Completely dissolves sediments and reduces emissions

Motorkote Catalytic and Exhaust Treatment

Last update on 2021-09-10 / Affiliate links / Images from Amazon Product Advertising API

Motorkote aka ‘America’s 1^st friction fighter’ is a powerful cleaner for the cat and the exhaust system. 

It ships in a bottle that resembles fine wine. That’s not the kicker though. 

This is one of the most effective catalytic converter cleaners that you can buy for the P0420 Catalytic Converter Code. 

The formulation contains powerful additives that reduce phosphorus & zinc retention levels at catalyst inlet, which is one of the primary causes for reducing the efficiency of the cat converter. 

Along with this, it also helps dissolve and flush out carbon deposits in the O2 sensor, which in turn helps reduce tail pipe emissions. 

There are tons of positive customer reviews that mention clearing emission tests, fixing the ‘check engine light’ and a marked improvement in the drive quality.

Better acceleration, fuel efficiency and reduced emissions are some of the differences that customers have noted. 

One full bottle is enough to clean extremely clogged cat converters in old vehicles. It’s only compatible with gasoline (petrol) engines though. 

Best features

• American brand
• Top rated cat converter cleaner for the P0420 code
• Powerful additives that reduce phosphorus and zinc retention
• Flushes out carbon deposits in the O2 sensor
• Reduces tail pipe emissions
• Use once in six months for maintenance

Honorable Mention – CRC Guaranteed to Pass Emissions Test Formula

Last update on 2021-09-10 / Affiliate links / Images from Amazon Product Advertising API

Finally, we have a brand that guarantees that you can clear an emission test with their catalytic converter cleaner.

That’s no mean feat given that there are probably millions of cars with cat converters that have layers of thick sediments on it. Never been touched, let alone cleaned professionally. 

This is the CRC emissions cleaner system. It’s a very basic additive-based cleaner that you add to the fuel tank and rev it up for a bit. After you drive around for a few miles, reset the code and you should be good to go. 

How does it work then? 

The formulation is stronger and contains detergent additives that scrub your entire fuel system. It removes carbon and varnish deposits that affect the performance of your car and trigger the error code. 

There will be a notable difference in the emissions of CO, HC and Nitrogen Oxide, which should help clear the emission test for both, tailpipe analysis and OBD II plug-in tests. 

And in case it doesn’t work for your car, you get double the money back. 

Now, there’s a process to claim a refund and we must say that it’s a little steep. That said, there are customers who have successfully claimed and gotten a refund. So it’s not mere marketing malarkey. 

Overall, we think that this is a very powerful cleaner and hence the bold claim and the guarantee. 

It should work pretty well for most cars unless you are trying to clean the exhaust system of an old clunker that has a million miles on it. 

Best features

• Guaranteed to work, else you get twice your money back
• Powerful detergent additives that scrub your exhaust system
• Improves combustion, reduces emissions of CO, HC and Nitrogen Oxide
• Should help clear emission tests (Both tailpipe and OBD II)
• Clear cat error codes and the rotten egg odor

How to Select the Best Catalytic Converter Cleaner

If this is the first time that you are shopping for catalytic converter cleaners, then this brief guide will help you narrow down on the right one for your intended application. 

Compatibility: Not all catalytic converter cleaning treatments are designed to work with hybrid and diesel engines. They all work with gasoline-powered engines though. So the first thing that you need to check is whether the brand you select is compatible with the type of engine in your car. 

Ease of use: Most catalytic converters are gas additives that need to be added to an empty fuel tank, before refilling it. However, there are some like the Motor Power Care converter kit and Liqui Moly, which need to be sprayed or applied directly to the intake tract. It’s reasonably easy. But some people are not comfortable with mechanical tasks. Others may not be able to perform these tasks themselves due to limitations. So, you might want to check the exact method of application and pick one that works for you. 

Complete cleaning: Some cleaners are designed to clean all the critical components of your fuel and exhaust system. If you suspect that the O2 sensor may be malfunctioning, or clogged as well with sediments, then look for a cleanser that cleans the entire system, as opposed to cleaning only the cat converter. 

Intended use: While all the cleaners in this list will help flush out gunk from your cat converter, there are some that are better suited for specific applications. Like helping clear an emissions test, or helping eliminate the rotten egg odor. We have tried our best to list these accordingly to help you select the best one for your intended use. 

Legality: Some additives are illegal to use in some states in America and you might want to check the legality of the product before you use it. 

Tips for an Effective Cleansing Routine

So, you’ve just bought a fancy bottle of the best catalytic converter cleaner. How do you use it? 

Here’s how. 

1. Read the instructions. While they all work in a similar fashion, the amount of gas that’s required in the tank before you add the cleaner might vary from brand to brand. Check the instructions. 
2. Most brands require you to have a nearly empty tank before you add the cleaner. Drive to the gas station and fill the tank up with the recommended amount. 
3. Get out on an empty road and rev the engine a little so that the exhaust gases are flowing through the system. Remember, the cat converter needs to get heated up to 400-500-degrees for the additives in the cleaner to start dissolving the gunk. 
4. Drive until you have an empty tank. Go back to the gas station and refill the tank. 
5. If the error codes haven’t reset automatically, do it manually. 
6. Congratulations. You’ve just cleaned the catalytic converter and possibly, the entire exhaust system. 

Catalytic Converter Cleaner FAQ 

Like we said at the onset, most car owners might not have tried something like this before. 

As a result, there are a lot of questions and a generous dose of skepticism about the effectiveness of the best catalytic converter cleaner. 

How does something that’s added to the gasoline tank fix a gnarling, persistent error like P0420? 

Miracle in a bottle?

This brief FAQ aims to answer some of the common questions that we’ve been asked by car owners about cat converter cleaners. 

Q. Are the best catalytic converter cleaners guaranteed to work?

A. Well, most of them are not. The CRC brand does guarantee it and offers a refund if it doesn’t. But to be honest, there are no guarantees that it will work because there’s no way to know the extent of sediments and residue that’s choking the catalytic converter in your car. Also, there’s a possibility that the converter might have melted or broken. In these scenarios, there’s no way any cleaning system will work. You have to swap the cat. Period. But if it’s not damaged, there’s a great chance that something like this will work and help you avoid a massive repair bill. 

Q. The ‘Check engine’ light goes off temporarily and then returns after a week or two even after applying the cleaner. Why?

A. You might need a second application of the cleaner. Most of the best catalytic converter cleaners in this list are designed to work in one application only. But at times, the damage is more severe than what can be cleaned in one go. Repeat an application if the light starts to flash again. If the problem persists after two applications, then you might have to inspect the cat or the O2 sensor for damage. 

Q. How are these better than the cleaning methods shown on YouTube?

A. For starters, none of these contain abrasive chemicals that will damage your fuel and exhaust system. But soaking your cat converter in acetone can potentially damage some of the rare and heavy metals that are used as the catalyst. Also, most of those methods require varying degrees of mechanical skills. The cleaners in this list are additives that need to be poured into the gas tank. That’s a no-brainer choice. 

Q. Will these help clear an emission test?

A. It most probably will. If your car fails the test due to poor emissions, then using the best catalytic converter cleaner is the easiest way to fix the problem. Not only will your emissions improve, it will also improve fuel efficiency and remove the offensive odors that are caused due to unburnt fuel.