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Published Sep. 25, 2018

Tucked away underneath the car, toward the very end of the exhaust system, you will find the catalytic converter. This is one of the hardest working but also underappreciated components on a modern car. Every journey you take it will be working hard to filter the engine exhaust gases of dangerous chemicals and compounds while also maintaining – or even improving – engine performance.

All it asks in return is for the occasional clean with a dedicated catalytic converter cleaner. Not only will this keep your converter happy, but it may also stop the dreaded “service engine” light flashing up on your dash display. We take a look at some of the best catalytic converter cleaners on the market and help you decide which one is the best to keep your exhaust gases safe enough to pass inspection and your engine purring.

The Best Catalytic Converter Cleaner

First is this entry from Cataclean, and there are a number of indicators that it is a premium product. The product has been tested in independent labs that show it to reduce hydrocarbon emissions by up to 50 percent. This is good news if your vehicle has failed an emissions test. A few doses of this bad boy and you stand a much better chance of passing the follow-up test.

This product also has a wide range of engine type compatibility. That is not something you see too often and is good news for diesel and hybrid vehicle drivers. Catalytic converter cleaner for these vehicle types is few and far between, so if you drive a non-gasoline powered vehicle, take a good look at this product.

We’re also pleased that this product is formulated to clean out the deposits that are clogging your converter as well as help limit those deposits from building back up again. That’s the kind of long-term protection that is always good to see and signals a product that represents a solid, long-term investment.

You’re not getting all that goodness on the cheap though, with one 16-ounce bottle setting you back a few bucks. It is available as a two and five pack for a bit better value, however. It’s also unsuitable for two-stroke engines, so don’t put this in your ride-on mower.

Key Features
  • 16-Ounce Pack
  • Formulated to Reduce Build Up
  • Cut Hydrocarbon Emissions by up 50%
  • Brand Mr. Gasket
  • Model 120007
  • Weight 14.4 oz

Cleans Engine & Catalytic Converter

Suitable for Gasoline, Diesel and Hybrid Vehicles

Helps to Limit Future Containment Build Up

Available as a Multi-Pack



Not Suitable for 2 Stroke Engines 

The emissions test is enough to raise the blood pressure of any car owner. If that sounds like you, you should check out our next product from CRC. It is a catalytic converter cleaner specifically formulated to help your vehicle pass the emissions inspection test. While that is certainly welcome news, just how does it achieve that?

In short, it does it by being a powerful cleaner. A really, really powerful one. It is designed to tear through deposits in your catalytic converter like Superman after he’s downed a case of Red Bull. The formula that makes up this product includes extremely powerful detergent additives that are designed to provide a deeper clean than other similar products on the market.

However, it will only work with gasoline engines, and the bottle is only 12 ounces – a pretty measly amount – so you may be best picking up a couple of bottles. The upside? CRC is so confident that its product will clean your converter enough for you to pass your emission test that it  has literally put its money where its mouth is.

If the vehicle fails after it has been treated with this product it will refund you twice what you paid to buy the cleaner. We come across a lot of companies that are understandably proud of their tools and products, but we have never seen anyone willing to back their product quite like this.

All in all, then this is an intriguing option with deep cleaning capabilities and a very interesting money-back guarantee.

Key Features
  • 12 Ounce Bottle
  • Highly Concentrated
  • Specially Designed to Pass Emissions Tests
  • Brand CRC
  • Model 05063
  • Weight 1 lb

Extra Powerful for Deep Clean

Pass your Emissions Test – or Double your Money Back!


Small Bottle

Gasoline Engines Only

Our next product is a cat converter cleaner from Solder-It. It comes in a big 16-ounce bottle at an affordable price. It is also available in a huge 12 pack for an even better per bottle price.

At its heart, this is your standard catalytic converter cleaner. It also has a built-in deodorizer function. This, combined with the standard cleaning operation, is designed to rid your car of that rotten egg smell that some cars acquire over time. That smell is actually caused by an ineffective engine that is allowing too much unused fuel to make its way through the system – plus a poorly maintained catalytic converter that is not filtering it out of the exhaust stream.

No one wants a car that smells like rotten eggs, so it’s great to see that this product is specially formulated to tackle that problem. This is a pretty simple and basic product.

It’s a slight concern that the manufacturers state that the product “may” help to pass the emissions test. After all, we’ve just looked at a product whose manufacturer is so confident in its abilities that it will refund twice your money if it doesn’t drag your vehicle kicking and screaming through the emissions test. With this product, however, you have to wonder if Solder-It doesn’t have complete faith in it why should anyone else? 

Key Features
  • 16 Ounce Bottle
  • Built-in Deodorizer
  • Brand Solder-It
  • Model CAT-1
  • Weight 1 lb

Good Value for Money

Tackles “Rotten Egg” Exhaust Smells


Very Simple Product

“May Help” Pass Emissions Test

Gasoline Engines Only

This product from Hi-Gear is designed to do exactly what it says on the can, which is tackle horsepower loss, improve efficiency, and reduce emissions of noxious gases. It cleans fuel systems injectors, combustion chambers, pistons, and valves. It also prevents vehicles from emitting that notorious rotten egg smell. 

This catalytic converter cleaner efficiently tackles hard starts, lost acceleration, and rough idling. This is not a product packed with bells and whistles, however. It has, for example, no ability to work with anything but gas engines – no cross compatibility here. What it does have is the cleaning power derived from a carefully formulated recipe that Hi-Gear has produced in collaboration with a number of vehicle manufacturers. This is not technically an OEM product, but it is about as close to one as you can get without actually being one.

There are no multipack options here either. You buy one can, you pour it into the tank and let it do its job. This product is ultimately very simple and very straightforward. But it is also designed to be extremely effective. That, to us at least, seems like a fair trade off.

Key Features
  • 15 Ounce Bottle
  • Tackles HP Loss
  • Simple but Straightforward
  • Brand Hi-Gear
  • Model HG3270s
  • Weight 15 ounces

Cleans all Parts of the Exhaust System

Tough Metal Can

High-Grade OEM level Formula


No Multipacks

Gasoline Only

In 2015, the VW emissions scandal was huge news. It turned out that Volkswagen, one of the largest European car makers, had been fiddling with emissions testing for its cars and for cars of manufacturers that VW owned, such as Audi. This caused a huge political scandal in Europe, one of the results of which was a massive tightening of air quality and exhaust emissions testing regulations.

You can now take advantage of that upheaval with this product from OXICAT. It is from Germany and is designed to help European car owners pass the new emissions testing processes. It does this by being a crazy powerful catalytic converter cleaner.

It is specially formulated to clean all parts and components of the exhaust system, not just the cat converter. In particular, it is formulated to clean the exhaust system oxygen sensors. That is great news because often a false reading from these sensors can trick you into repairing a fully functional cat converter – costing you time and money.

It’s also worth pointing out that this is one of the few products suitable for use on a wide range of engine types, so hybrid and diesel drivers take note. This is clearly a high-end, premium product with a somewhat high price tag to match. Still, it is undoubtedly a well-engineered product, and whether it’s worth its price tag is up to you.

Key Features
  • Works on Petrol & Diesel
  • Formulated to Clean the Whole System
  • Model 43243-1
  • Weight 10.1 oz

Works on Lots of Engine Types

Formulated to Meet Stringent EU Standards

Dissolves Soot & Carbon Buildups Across the Entire System



Small Quantity of Product

No Multipack Options

Best Catalytic Converter Cleaner Buying Guide

How can you decide which of these great products are going to be the best for you though? Well, in this next section we will go through some of the features that you should expect to find in the best catalytic converter cleaner products. After that, we’ll take a quick look at all the benefits of these awesome products, as well as show how to use them effectively.

We’ll finish up with the answers to some of the most frequently asked questions about catalytic cleaners and you should be fully equipped with everything you need to have the cleanest catalytic converters on your block.

What To Look For In the Best Catalytic Converter Cleaner

  • Full System Cleaning – The best cleaning products should be capable of cleaning the full exhaust system and not just the cat converter itself. This will be helpful because the exhaust system is, well, it’s a system. That means each part of the system is as important as the next. The oxygen sensors, for example, are placed at the entrance and the exit of the catalytic converter chamber. They monitor airflow and also how effective the converter is performing. A false reading can lead you to pay a lot of money you don’t have to replace a clean converter. That’s just one example of why you should try to keep the whole system clean.
  • Multipack Options – They may not be the most expensive products in the world, but we’re sure you can still think of plenty of things you would rather spend your money on, right? A multipack is a great way to keep the cost down, especially as this is a product you need to use as part of your regular car maintenance.
  • Engine Compatibility – If you drive a regular gasoline-powered car, you have nothing to worry about, since almost all catalytic converter cleaner products will work with your vehicle. If you drive a hybrid or a diesel-powered vehicle though then you must check the engine compatibility. Premium cleaners will be blended to be suitable for a range of engine types, so keep an eye out for that if you need it.

Benefits of Using Catalytic Converter Cleaner Additives

To our mind, there are several reasons why you should consider investing in a bottle or two of the catalytic converter.

  • Fighting Smells – You may have seen it mentioned in a couple of the reviews up top that some catalytic converter cleaners are specially formulated to tackle that nasty rotten egg smell that some cars can develop. That smell is just due to a build-up of containment in the cat converter that is stopping it from filtering un-burnt fuel from the exhaust stream. So if your car smells like eggs, a cat converter cleaner can be a cheap and easy solution.
  • Improve Performance – One of the big indicators of a clogged cat converter, aside from the old service engine fault lights on the dash display, is a loss of engine power. You will especially notice this when you are climbing an incline or when you are starting the vehicle forward from a dead stop. This is because a clogged catalytic converter will not allow exhaust gases to flow and vent properly. This, in turn, affects engine performance as it starts to get backed up with unvented gases. Bad news all around. By the way, some people think it’s smart to remove the converter altogether to improve performance. Don’t do that. The engine system – including the exhaust system – is a finely tuned machine. Simply ripping part of it out is not the way to improve it.
  • Cash Saver – Somewhat connected to the point above, an efficient catalytic converter can keep dollars in your purse or wallet. For one thing, as we just mentioned, it improves performance, raising the miles per gallon you can squeeze out of the car. The second reason is that a catalytic converter is expensive! It is far, far cheaper to invest in a regular clean with one of the products we looked at above, rather than to be hit with a huge replacement bill further down the line.
  • Clean Air – Finally, catalytic converters are in the car for a very good reason – to filter the exhaust gas and improve air quality for everyone. That may sound like touchy-feely liberal junk, but it is true. We all breathe the same air after all – you, your partner, your children, and your family. Air quality in the US is about 70% better today than it was 50 years ago. That means less kids with asthma and less seniors with oxygen tanks. Unless you are literally the dark lord himself that can only be a good thing. A clean catalytic converter is an effective catalytic converter, so use these products to keep it clean so it can carry on doing its job.

How to Clean Catalytic Converters

One of the joys of catalytic converter cleaner is how simple it is to use. There really is no need to bust out the full toolkit, in fact, all you need to do is to go to the gas station and, well, buy some gas.

We will give you the same advice we give you on every article we write and that is to check the instructions for the product you have chosen. Broadly speaking they all work the same, and all you have to do is pour the cleaner into your gas tank. However, there can be a difference in how much gas you need in there before using the cleaner so again, and we don’t mean to nag, read the instructions!

In our experience, most cleaners will state that the tank should have about four or five gallons of gas left before adding the cleaner. We recommend you empty the tank as much as possible then drive to the gas station and top up with the amount of gas recommended in the instructions on your product.

After you’ve done that, drive normally until the tank is empty. For best results, try to get out on the freeway so you can get a good solid stream of exhaust gases going through the system. When the tank is empty again simply refill as normal and you’ve got yourself a makeshift bird feeder, sir.

Checks notes.

No, sorry. You have a clean catalytic converter, that’s what you have.

Also, if you’re looking to unclog a catalytic converter that is really gummed up, it may take a couple of cycles of cleaner to get the converter sparkling clean again. If you are still having issues after a couple of cycles then the damage may be too severe for the cleaner to reverse. Considering the price difference between a bottle of cleaner and a brand new cat converter though it is well worth trying the cleaner first.

What Causes Catalytic Problems?

Catalytic problems are caused by the catalytic converter doing its job too well. Seems a bit unfair, huh?

Below, in the FAQ section, we go into how a catalytic converter works, so we won’t go into it again here. Suffice to say that, when the cat converter does its job, it captures, amongst other things, carbon and stops them puffing out into the air behind the car as part of the exhaust.

Catalytic problems occur when the converter is starting to get too clogged up with carbon and other nasty deposits. It is a simple problem to fix, however – simply flush the exhaust system with the best catalytic converter cleaner you can find and all should be well.

Best Catalytic Converter Cleaner FAQ:

Got a question about catalytic converter cleaner? You’ll probably find the answer below…

Q:  How does a Catalytic Converter Cleaner work?

  Since 1975 it has been the law that every car in the US has to be fitted with one of these devices to help filter the vehicle exhaust gas. A converter does this by being a catalytic converter. No, this isn’t a weird riddle. We’re just saying that the clue is in the name, so let’s break it down. A catalyst is a chemical, compound or a metal that is designed to create a chemical reaction. The catalysts inside your converter are three rare metals – Platinum, Palladium, and Rhodium. These are all contained inside a ceramic honeycomb style of structure. The exhaust flows through this ceramic box, and the bad things in the exhaust like Hydrocarbons and un-burnt fuel react with the three metals. Those metals (which are “Catalysts” remember) then “Convert” all the bad stuff into normal things like Carbon Dioxide and Nitrogen – both gases which are already present in your breath, i.e. they are not harmful. So to summarize, a catalytic converter works by using catalysts to convert bad crap in the exhaust into less bad stuff. That’s also by the way you need to clean the thing so often because of all those nasty chemicals and compounds – mainly carbon – get left behind inside your converter. They clog it up and stop it from doing its job. The way the converter actually works, on a chemical level, is pretty high tech and confusing. All we as car owners need to know is that bad air goes in one end, and slightly less bad air comes out the other.

Q:  How often should I use a Catalytic Converter Cleaner?

  Catalytic converter cleaner often gets a bad rep because people use them too late. They drive around for thousands of miles, oblivious to the build-up of carbon and other nasty deposits in the cleaner. They then notice a rotten egg smell, a loss of horsepower on inclines or slower acceleration from a standing start. They throw a bottle of catalytic cleaner into the gas tank and expect it to sort out all their problems. In some instances it does, because they have, by accident, caught the problem early (or early-ish at any rate) and the cat converter just needed a good clean. In many instances, though the damage is already too severe. A catalytic converter should not be looked at as a mechanic-in-a-can. Instead, it should be part of the ongoing maintenance regime of the car – the same as changing the oil or replacing the brake pads when they are worn. We would recommend that if you’ve never cleaned your catalytic converter before that you do this as soon as possible. After that, consider cleaning it again roughly every 3,000 to 4,000 miles. Bearing in mind that a new cat converter can set you back hundreds of bucks, that little bit of regular maintenance will pay for itself many times over.

Our Top Pick

Whilst there are a number of fine products on this list, we can’t look past the Cataclean Engine & Catalytic Converter Cleaning Treatment as the best catalytic converter cleaning product out there right now. Yes, it’s not cheap and generally, we avoid picking the most expensive product as the top pick if we can avoid it.

That said, it’s still just 30 bucks per bottle, and the multipack options bring the per unit price down even further. For that price, you get a product that cannot only unclog catalytic converters but also works to limited build up in the future. We like a product that offers long-term protection as well as short remedies. Add to that the fact it works on just about any engine – gasoline, diesel, and hybrid – and that should give you a good idea why we rated this product so highly.


  1. Catalytic Converter, How Stuff Works
  2. VW Emissions Scandal, Autocar


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