What Is a Catalytic Converter Cleaner, and Does It Actually Work?

Rather than a furry little friend that wakes one up at five in the morning for snuggles and wet food, cat stands for catalytic converter in this particular context. Regardless of the vehicle operator's driving habits and the design of a given catalytic converter, this device will eventually start losing performance.

In this case, trying a cleaning solution is the way to go. Will such a cleaner actually revive the catalytic converter, though? Before answering this question, we first have to understand how a catalytic converter works and why it becomes clogged with time.

How does a catalytic converter work?

First and foremost, a cat should not be confused with a particulate filter. The one and only Alan G. Loofbourrow famously said, "[The catalytic converter is] the dumbest thing that ever happened to the automobile." Coming from the chief engineer of the Chrysler Corporation's program in the development of the atomic bomb during World War II, those words once carried a lot of weight.

Be that as it may, Loofbourrow said the aforementioned from the point of view of an engineer with great knowledge in all phases of automotive design. One who searches for improved performance with minimal penalties in gas mileage and production costs will obviously be against an apparatus that hinders the engine's ability to make power.

The ability of an engine to make power is related to how efficiently it combusts the air-fuel mixture and how efficiently it rids itself of the by-products of combustion. With the catalytic converter in the way, it should come as no surprise that all new vehicles available today could be punchier without cats.

As implied by its name, the catalytic converter is designed to convert the nasty stuff resulting from the combustion process into less toxic stuff by catalyzing a redox reaction. In the beginning, cats featured a two-way design that enabled the oxidation of carbon monoxide into less harmful carbon dioxide, along with the oxidation of unburned hydrocarbons into carbon dioxide and water. This design's ineffectiveness to reduce nitrogen oxides led to the development of the three-way cat.

The front honeycomb piece of a three-way catalytic converter is coated in a precious metal called rhodium. Its role is to break down the NOx into nitrogen and oxygen. Three-way plus air converters were phased out in the early part of the 1980s in favor of the simpler three-way catalytic converter as we know it today.

We also have to mention diesel oxidation catalysts, which are – obviously enough – used in diesel vehicles. Just like the two-way catalytic converter, they're not good at reducing NOx. To this effect, a modern diesel aftertreatment system includes a diesel oxidation catalyst, a particulate filter, and selective catalytic reduction. The latter system converts NOx into diatomic nitrogen and water with the help of diesel exhaust fluid, a solution that contains deionized water and urea.

In addition to rhodium, three-way cats further contain palladium and platinum. This, in turn, explains why catalytic converter theft is on the rise in the United States. Taking a reciprocating saw to cut the cat from the exhaust system is simple enough, and it's even more simple on vehicles with high ground clearance. Think body-on-frame trucks, Jeep Wranglers and Ford Broncos, and so forth.

Anti-theft devices exist, and they're not particularly expensive. Physical barrier is the name of the game, with said barriers coming in many flavors. Outside your typical shield or cage, theft prevention also takes the forms of the Pop & Lock Cat-Rap, Catstrap, and CatClamp. A catalytic converter shield usually starts at 100-plus bucks, albeit you are better off paying extra for a high-quality product.

Certain automakers offer catalytic converters directly from the build & price tool. Toyota comes to mind with the fifth-gen Prius. As of this writing, the MillerCAT-branded cat shield carries a sticker price of 150 buckaroos.

Cleaning a catalytic converter

Carbon monoxide, unburnt hydrocarbons, and nitrous oxides pass over and through the honeycomb pieces of the catalytic converter. In combination with the right amount of heat, the precious metal-coated substrates of the cat do their thing, converting the pollutants and toxic gases into less harmful gaseous emissions.

As you might have guessed by now, the catalytic converter will inevitably get clogged from the oxidation–reduction reactions. There are quite a few other things that could make a cat lose its redox performance, including a too lean or too rich air-fuel mixture, bad oxygen sensors or wiring, and physical damage. In case of damage, replacement is the answer.

The symptoms of a bad cat include a noticeable loss of power, hard starts, a drop in fuel economy, and the smell of rotten eggs. Also worthy of note, P0420 and P0430 are codes that indicate three things, beginning with iffy wiring or a bad oxygen sensor. The worst-case scenario is a bad catalytic converter.

Some peeps recommend pouring lacquer in the fuel tank in order to clean a debilitated cat, which is a pretty bad idea. Then again, the Internet is full of nutty DIYs that could ruin your vehicle. Because most fuel tanks and pumps use plastic components, thinner creates more problems than it actually solves. Also remember that lacquer thinner contains quite a bit of acetone that the engine burns, thus defeating the purpose of using lacquer thinner to clean a clogged catalytic converter.

Submerging the catalytic converter into a soapy water solution is another oft-recommended fix, along with pressure washing and spraying carburetor cleaner to remove stubborn deposits. These procedures require cutting off the cat from the exhaust system, then welding it back with no guarantee of restoring the cat's efficiency.

Looking at the bigger picture, the least labor-intensive way of addressing this problem is to try a specially formulated catalytic converter cleaner from a known brand. But more on brands later. Once again, it's extremely important to highlight that catalytic converter cleaners are not guaranteed to restore your cat's performance. Tutored by Aristotle until the age of 16, the overly ambitious Alexander the Great is credited with saying, "There is nothing impossible to him who will try."

He wasn't referring to cleaning a cat, but hey, the Hellenic schools of thought transcend into modern beliefs and values at every single level. Most professional cleaners are to be poured into the fuel tank. Said cleaners travel through the fuel pump, engine, and catalytic converter, which is why they also clean – supposedly – the fuel injectors, valves, combustion chambers, exhaust gas recirculation passageways, and oxygen sensors.

"Helps" is one of the most common words used in advertising said products. The fine print is even more telling, but do not mistake said products for snake oil. Liqui Moly sells a product that has to be sprayed in the intake tract rather than poured into the fuel tank.

With the engine running, Catalytic-System Clean has to be sprayed into the intake tract in short intervals at medium engine speeds. Liqui Moly clearly states that Catalytic-System Clean does not remove manganese oxide deposits from the catalytic converter.

Popular catalytic converter cleaners

Just under $20 is the retail price of the Catalytic-System Clean at press time, with said product coming in a 300-milliliter aluminum can with a blue plastic cap. In old money, that would be a little over 10.1 fluid ounces.

Owned by Wurth, the German company advertises an immediate and measurable reduction of pollutants. Catalytic-System Clean is also said to protect the catalytic converter from clogging with soot.

Cataclean hails from the United Kingdom, yet it's hugely popular in the United States of America. Part of the reason is aggressive marketing, and the other part is a five-strong lineup of cleaners. More specifically, Cataclean offers cleaning solutions for gassers, diesels, and hybrids. They also developed cleaning solutions for motorcycles and lesser powerplants, namely those used in generators, lawnmowers, trimmers, and chainsaws.

The gasoline, diesel, and hybrid cleaners are priced at 16.99 pounds sterling back home in the United Kingdom. Over in the United States and Canada, these products are distributed by Holley. The company recommends using their products every three months, with Cataclean promising an 8-in-1 cleaning effect.

Cataclean ships in 500-ml bottles that are to be poured into the fuel tank at a ratio of 500 milliliters (16.9 ounces) to 15 liters (4.0 gallons) of dinosaur juice. After that, simply drive your vehicle for at least 15 minutes.

Dura Lube Severe Catalytic & Exhaust Treatment is another good pick. The instructions recommend using the product when the warning light comes on, with a full bottle good for 16 gallons (60 liters) of fuel. In severe cases, an entire bottle should be used only if the tank is at least a quarter full.

Similar to Cataclean, the folks at Dura Lube recommend using their product every three months. Dura Lube states that Severe Catalytic & Exhaust Treatment helps pass emission tests by cleaning the exhaust system and removing carbon deposits in the catalytic converter.

CRC Industries Guaranteed To Pass Emissions System Cleaner is a special product, for CRC will double your money back if you don't pass the smog test. One bottle added to a half-full tank should do the trick. Priced at $14.99 per 12 fluid ounces, CRC Industries Guaranteed To Pass Emissions System Cleaner dissolves sludge in the fuel system and removes deposits by means of a powerful detergent formula.

Hi-Gear EZ Emissions Pass & Catalytic Converter Cleaner is the final product we'll cover. Yet another one-tank smog test pass, it costs 13.99 pounds sterling per bottle. Simply add the cleaning solution to a quarter tank of fuel and drive as normal for 15-odd minutes.

Replacing a catalytic converter

Before spending big money on a replacement catalytic converter, do retrieve all diagnostic trouble codes and repair as necessary. Also check for any technical service bulletins and powertrain control module software updates. Furthermore, check the exhaust manifold and the rest of the exhaust system for improper alignment, damaged gaskets, and cracks.

Replacement cats are split in two categories. Direct-fit catalytic converters are designed specifically for the make, model, and model year of a given vehicle. Universal catalytic converters, meanwhile, are that little bit harder to install. When it comes to emission regulation standards, replacement catalytic converters are EPA- or CARB-compliant.

The states of California and Colorado have the strictest emission standards in the nation, with both states requiring model year 1996 and newer vehicles registered in their jurisdiction to be equipped with CARB compliant catalytic converters. That being said, how much does a replacement catalytic converter cost?

For example, an OEM-grade cat for the 2014 model year Subaru BRZ sports coupe is anything between $194 and $1,190 on MagnaFlow's website. $194 buys you a universal catalytic converter, which requires cutting and welding. By OEM grade, MagnaFlow refers to performance and quality similar to that of the original catalytic converter.

$763 gets you a direct-fit assembly that comprises the cat and mandrel-bent tubing. It replicates the original's spun body design. MagnaFlow recommends using the included gaskets to avoid potential exhaust leaks.

Last but certainly not least, $1,190 is the retail price of a direct-fit manifold catalytic converter. All three replacement cats are compatible with the mechanically similar FR-S from Scion and the 86 from Toyota.

Diesel and gasoline particulate filters

Particulate filters can be easily mistaken for catalytic converters by those with little inclination for all things automotive. The biggest difference between particulate filters – be it DPFs or GPFs – and cats? That would be how they work. While the catalytic converter changes the chemical composition of the exhaust gas, the particulate filter is best described as a trap for particulate matter.

Captured particles are burned off through passive or active regeneration. Similar to catalytic converters, particulate filters will eventually need replacing. DPFs have a reputation for getting clogged on vehicles used mostly for short journeys at predominantly low engine speeds. Gasoline particulate filters don't clog as easily. Not only do gassers emit lower volumes of particulates, but their exhaust gas temperatures are higher to boot.

US EPA Tier 4 emission standards will see light-duty vehicles adopt gasoline particulate filters by 2030. The GPF became ubiquitous in the Old Continent and China with the introduction of Euro 6 and China 6 regulations. Both introduced a particle limit for gasoline exhaust, with GPFs building on the wall-flow technology of diesel particulate filters.