Best Catalytic Converter Cleaner

My Guide to The Best Catalytic Converter Cleaner

It’s time for your car to have a emissions inspection and it fails.

They tell you that you need a new catalytic converter, commonly called a “cat”.

A new cat converter is a few hundred dollars! How can yours possibly be bad? Your vehicle doesn’t have that “rotten egg” smell!

Cats do wear out over time. But they are under warranty for a minimum of 10 years from the manufacturer. If your vehicle is less than 10 years old, call your dealership to see if your car, truck, or SUV qualifies for a free replacement.

Otherwise, there is one more trick you can try before you shell out some big money for a replacement cat.

A catalytic converter cleaner.

Maybe you are skeptical. You have every right to be. But the truth is that sometimes, these products work.

By pouring a can or two into the gas tank and driving your car, you can remove some of the carbon and tar buildup inside the cat.

Which is the best catalytic converter cleaner? I will tell you everything you need to know next.

My Winner: Cataclean Complete Engine, Fuel, and Exhaust System Cleaner

Cataclean is the best known cat converter cleaner. It can lower the overall total hydrocarbon emissions of your vehicle by as much as 50 percent!

This is a premium cleaner that will remove carbon buildup and grime from the cat, the O2 sensors, fuel injectors, and more.

This will go a long way towards not only allowing your vehicle to have a better chance of passing an emission inspection, but to help it have improved fuel efficiency.

Hard starting, power loss, a Check Engine light that is on, and a reduction in fuel economy are all signs that the fuel and exhaust system needs cleaning.

Cataclean will remove deposits and help your ride run better than ever.

Keep in mind that this is not for 2-stroke or gas mix engines, but it works fine in diesel engines.


  • It works in most cases
  • It’s relatively inexpensive
  • It’s easy to use, just pour and run


  • It’s not a 100% slam dunk. There are some cases where Cataclean won’t work.

That really was the only drawback I could find. If your cat is too far gone, if you hear a rattling noise from the cat, or if the outside casing has rusted through, it’s time to buy a new cat.

Even Cataclean can’t fix some converters.

If you are trying to decide whether to replace the cat or not, I highly recommend using Cataclean. You can find detailed instructions on how best to use it below.

You have nothing to lose and a bunch of money to save by trying Cataclean first.

Runner Up: Berryman Emissions Pass Protection

Berryman’s is a well known name in automotive additives. Their Emissions Pass Protection additive – well, the label says it all.

This fuel additive is designed to allow your vehicle to pass an emission test.

It reduces hydrocarbons, carbon monoxide, and nitrogen oxide by cleaning combustion chamber deposits, intake valves, fuel injectors, and more.

I like Berryman’s fuel additive because it has a money-back guarantee. If your vehicle doesn’t pass smog after using it as directed, you get a full refund! Now that’s confidence!


  • It’s very inexpensive
  • The long neck bottle makes it easy to add to the gas tank
  • It has a money-back guarantee


  • The product doesn’t specifically state that it cleans the catalytic converter

Like Cataclean, this product says that it will reduce emissions so that you pass a smog check. It doesn’t’ say that it will clean up the catalytic converter. If the cat is your main problem, it is unclear if this will work.

However, with a money-back guarantee, you have zero to lose other than a small investment in time.

Honorable Mention: Hi-Gear Emissions Pass and Catalytic Converter Cleaner

The Hi-Gear name isn’t as well known as Berryman’s or Cataclean, but the information I’ve heard about this product rates it as an honorable mention.

Like Cataclean, this product is designed to clean the entire fuel and exhaust system, including the catalytic converter.

Note that this is ONLY for gas-powered engines and cannot be used for diesel engines.

If your vehicle has failed an emissions test or if the Check Engine light keeps coming on with codes that indicate that the cat is failing, you might want to try Hi-Gear Emissions Pass.


  • It’s inexpensive
  • It’s easy to use
  • It appears to work for most people


  • The product is not as well known as others
  • Doesn’t work for everyone
  • The container is difficult to open

Keep in mind that the catalytic converter must be in good condition and not rusted through or have a loose honeycomb insert for this product to work.

Unlike Berryman’s this product doesn’t have a money back guarantee. But it’s cheap enough that you won’t feel cheated.

When you need to clean your cat and you don’t want to pay for a brand name like Cataclean, Hi-Gear gets high marks for lots of positive reviews.

Does Catalytic Converter Cleaner Really Work?

Yes, they work. But not in every case.

While it’s a fact that catalytic converters build up dirt and carbon, the truth is that everything in life, including cats, wears out with age.

You can always try to use one of the catalytic converter cleaners mentioned above and use it as directed. If it helps some, repeat the process.

If the converter has rusted through the outside layer, or if you can hear rattling noises from the cat, these are signs that the honeycomb interior has broken off or broken apart.

The cat will need to be replaced. No amount of fuel additive will reverse these problems.

Also, if your vehicle is still having issues after one or two doses of catalytic converter cleaner, it’s time to replace the converter.

If the catalytic converter cleaner works and your vehicle is running fine again, you might want to consider using this twice a year (depending on how much you drive) to keep the cat clean and clear.

Can a Clogged Catalytic Converter be Cleaned?


Yes, a clogged catalytic converter can be cleaned in most instances.

But not always.

The honeycomb mesh of materials inside the cat can become coated with carbon and other deposits. That may cause your car to fail a smog check and run poorly.

If the only real problem is a dirty converter, then running a can or two of one of the above catalytic converter cleaners is the perfect solution to solve your problem.

But if the honeycomb mash should break away from the converter housing, or if the outside housing has rusted to the point that it leaks or it cannot be connected to the exhaust pipe, all the converter cleaner in the world is not going to help.

How Long Does it Take for Cataclean to Work?

I suggest a 15 to 30 minute car ride for Cataclean to really work.

Cataclean is one of the best-known cat cleaners on the market. This product is super popular because it is easy to use and it really works.

To use Cataclean, fill up your gas tank and then dump the entire bottle of Cataclean into the tank.

Drive the car for at least 15 minutes.

But to be honest, a 30-minute drive would be better. Be certain that you keep the RPM over 2500. This gives your car plenty of time to fully warm up and get some of the product into the catalytic converter.

If you had error codes, this would be the time to clear them out or to ask your mechanic to clear them. Drive another 50 miles to ensure that the Check Engine light does not turn on.

Drive the car until you hit the ¼ tank mark, then refill the gas tank.

Your catalytic converter should be completely clean and your ride ready for your emissions test.

What are the Signs of a Clogged Catalytic Converter?

Most people don’t know that the catalytic converter on their ride is failing until that Check Engine light turns on or when they fail their emissions test.

The cat does give you some warning signs in advance that it is dirty and ready to bite the dust.

Some warning signs are:

  • Excessive heat from under the vehicle or the car runs very hot
  • Reduced acceleration
  • Sluggish engine performance
  • Dark colored exhaust
  • The very strong smell of rotten eggs or Sulfur from the exhaust
  • Difficulty starting the car
  • Poor fuel economy
  • The Check Engine Light comes on
  • Misfiring or rough running
  • A rattling sound from underneath the vehicle

Keep in mind that some of these signs can be other problems such as the need for a tune-up, a dirty O2 sensor, or other emission part failure.


We all would love our cars to simply run forever and never need anything more than gas and the occasional oil change.

But this is real life we are talking about.

Over time, your cat will simply become so clogged with carbon and other byproducts of exhaust that it becomes too dirty to work properly.

If that is the case, you don’t need a replacement cat. All you need is a can or two of Cataclean.

This is the best darn catalytic and fuel system cleaner on the market. You will find that nearly all users say that this product saved them hundreds on a new cat.

This will also clean up other items that get clogged, including those dreaded O2 sensors.

You will need to clear the engine codes after using Cataclean for you to pass an emissions test. But after that, your ride should have no problem passing if the only problem is a dirty catalytic converter.

Try Cataclean on your vehicle. Seriously, if it doesn’t fix your problem, your cat is not salvageable.

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