You may never think about this component of your vehicle, but the catalytic converter cleans your engine’s exhaust by turning the exhaust gases into other gases that are less harmful to people and the air. It’s a high heat process in the dirtiest part of your vehicle, and that can, over time, cause buildup and even clogging in your catalytic converter, meaning that it does less, well, converting. That could be why you’ve failed a smog test or why that check engine light is on.

Whether it’s because of a check engine light that won’t go away, or a failed emissions test on a vehicle that seems otherwise in good condition, rather than spend a load of money on a new catalytic converter, trying to clean the one you have is always worth a go. Since you can’t use a brush to clean out the cat, your best bet is to try and use one of these catalytic converter cleaner additives.

To learn more about the best catalytic converter cleaners, refer to our table of contents.

1. Editor's Pick: DURA LUBE Severe Catalytic and Exhaust Treatment

DURA LUBE Severe Catalytic and Exhaust Treatment

DURA LUBE Severe Catalytic and Exhaust Treatment is designed to treat your catalytic converter from oil poisons. The manufacturer says that it helps to clean your system, meaning that it will remove buildups and contamination that are causing your catalyst to lose efficiency, which can cost you power and money as well as dirtying the air that flows out the back.

It also helps to lower phosphorous and zinc retention at the inlet of the catalyst, both of which can cause premature poisoning and failure of a catalytic converter. This should help clean OBD error code P0420, which is the one that tells you your catalytic converter isn’t operating and cleaning as it should. One bottle lasts up to 5,000 miles (or three months), adding one bottle to the fuel tank for up to about 15.9 gallons of gasoline. The product is also safe for engines using diesel and ethanol-containing flex-fuels.

Product features:

  • Long-lasting
  • Protects catalyst from long-term poisoning from phosphorous and zinc
  • Helps clear engine codes

2. Cataclean

Cataclean 120007 Complete Engine, Fuel and Exhaust System Cleaner

Cataclean by Mr. Gasket can get rid of carbon buildup in your catalytic converter. That’s the type of contamination that can be caused by a poorly running engine (think old spark plugs or a leaky fuel injector), which won’t necessarily be removed even when you fix the other problems in your engine. Instead of needing a new cat because your engine ran rich for a while, use Cataclean to help get that carbon out.

It can fix drivability issues, too, because that carbon can choke your converter making it hard for the engine to breathe. Low airflow from clogging increases pollution, hurts power, and ruins fuel economy. Cataclean claims it can lower hydrocarbon emissions up to 50 percent, making your car, truck, or SUV less of a polluter as it ages. This cat cleaner also cleans your fuel injectors and cylinder heads, helping remove power-starving and engine harming buildups in those components as well.

Product features:

  • Removes cat carbon buildup
  • Cleans fuel injectors and cylinder head
  • Reduces emissions

3. Solder-It Catalytic Converter Cleaner

solder-it catalytic converter cleaner

A failing or poorly-operating catalytic converter can lead to a rotten egg smell in your exhaust. That’s related to part of the function of the device, where harmful hydrogen sulfide is turned into sulfur dioxide. This is less important than in the past thanks to low-sulfur fuels, but it hasn’t completely disappeared. So if you’re getting that rotten egg smell, there’s a problem with the cat. Or you need to remove your old lunch.

This fuel additive can help to “scrub” the inside of your catalytic converter, removing the deposits that are preventing it from working correctly. Used as directed, it can also help clean your oxygen sensors, making sure that they’re reading correctly as well as extend the time between needed tune-ups. On older engines, you can pour this directly into a running engine’s carburetor to let it work even more quickly than it would diluted in a fuel tank.

Product features:

  • Helps stop rotten egg smell
  • Helps clean oxygen sensors
  • Works with all catalyst types

4. Hi-Gear EZ Emissions Pass and Catalytic Converter Cleaner

Hi-Gear HG3270s EZ Emissions Pass

Again, you’re looking at that check engine light that comes on occasionally, but you’ve fixed everything short of the thousand-dollar cat? Give EZ Emissions Pass a go. Hi-Gear says that it works with additive manufacturers and OEMs to have access to some of the latest technologies available. This product is designed to clean the cat of carbon deposits as well as to help remove that rotten egg hydrogen sulfide smell.

Thanks to a double-action formula that also works to clean the combustion chamber, remove deposits from your EGR valve, and the rest of your fuel system, it can work to improve overall vehicle performance. More than cleaner emissions, it can help restore fuel economy, power, and throttle response, making your vehicle all-around better than before. The manufacturer says that one can treats up to 20 gallons of fuel, and that you should use it regularly to ensure peak performance.


  • Complete fuel system treatment
  • Removes catalytic carbon deposits
  • For gas engines only

5. CRC Guaranteed to Pass Emissions Test Formula

CRC Guaranteed to Pass Emissions Test Formula

Guaranteed to pass. It’s a bold claim, but the manufacturer says that you’ll pass your emissions test or get double your money back. That’s because it will reduce carbon monoxide, hydrocarbon, and nitrogen oxides emissions. The powerful detergents in the mixture will remove carbon and varnish deposits from the fuel system, allowing everything to run more smoothly and more cleanly than before. The steps are simple, pour a bottle into a tank of gas, run that tank down to close to empty, then fill your tank back up and they guarantee you’ll pass.

Of course that guarantee only applies if the rest of your car is running correctly and the engine is stock: it won’t fix that broken fuel injector or disconnected oxygen sensor. While it’s easy to be skeptical of claims like this, there are plenty of happy reviews from customers with vehicles that were otherwise working well but not passing emissions using the product and coming back to successful results.


  • Cleans fuel system as well as cat
  • Double money-back guarantee
  • Reduces emissions

Why Do I Need Catalytic Converter Cleaner?

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Years of low quality gas, engine problems you waited too long to repair, and general vehicle age can all lead to the deterioration of catalyst efficiency and lead to carbon buildup and clogging inside the complex innards of your catalytic converter. As long as the internal structure hasn’t physically broken down, there’s a chance that one of these additives can bring it back to proper function. That cleans the air coming out of your exhaust, reducing pollution and keeping toxic materials out of the air you breathe. If that catalytic efficiency check engine code keeps popping up, and it’s all alone, a catalyst cleaner is your best place to start before spending thousands to replace that expensive can full of precious metals under your car.

How Often Should I use a Cleaner?

Follow the manufacturer’s recommendations, but once per oil change is often enough. On older cars, which produce more emissions than later models, more frequent use may be needed to keep your cat working better down the road.

Will it Fix my Clogged or Broken Catalytic Converter?

If it’s completely clogged inside, or, worse yet, the catalyst material has broken down into pieces inside the exhaust (tap it with a soft hammer and listen for internal rattling), then nothing in a bottle can bring it back to life. In that case, you will need to replace your converter, but for smaller issues these cleaners could be wallet saving.

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