Nothing inside moves and it has no service interval, so it can last for years, though the catalyst, the metal coating that does the chemistry, slowly loses strength with age. It can also cost more than any other single part on the exhaust, because what a converter costs is set by what is painted on the inside.
What is a catalytic converter and what does it actually do?
A catalytic converter is a metal can in the exhaust that turns harmful gases into less harmful ones as they pass through. Engines produce carbon monoxide, unburned hydrocarbons and nitrogen oxides, and the converter deals with all three, which is why the modern one is called a three-way converter.
Two of those jobs are oxidation: adding oxygen to carbon monoxide and to unburned fuel so they leave as carbon dioxide and water. The third is reduction, and it works the other way, stripping oxygen back out of nitrogen oxides so they leave as plain nitrogen.
The oxygen sensors measure the oxygen left in the exhaust. The engine computer uses them to hold the air to fuel ratio so tightly, because the converter only works at the right mixture.
What metals are in a catalytic converter?
Platinum, palladium and rhodium. Platinum and palladium handle the oxidation, and rhodium, the most valuable of the three, handles the nitrogen oxides.
Platinum and palladium do much the same job, and palladium has replaced most of the platinum in gasoline engines for a plain commercial reason: it was cheaper when the switch happened. The US Geological Survey notes that palladium substitutes for platinum in most gasoline-engine converters because it cost less.
Rhodium does a different job: it breaks down nitrogen oxides. It's also by far the most expensive of the three per troy ounce, the unit of about 31 grams that precious metals are priced in, by USGS estimates for 2025.
| Metal | What it does |
|---|---|
| Rhodium | Handles the nitrogen oxides |
| Platinum | Cleans carbon monoxide and unburned fuel |
| Palladium | Does platinum's job, at a lower price |
The metals are a thin coating, not solid parts. A ceramic block inside the can is extruded into thousands of parallel channels, and a rough coating on it carries the metals and gives the gas an enormous surface to touch.
Use this image
Free to republish under CC BY 4.0: credit Oil & Miles and link to this page. The snippet does both.
<a href="https://oilandmiles.com/articles/what-is-a-catalytic-converter"><img src="https://oilandmiles.com/assets/img/diagrams/what-is-a-catalytic-converter-cutaway-r3.svg" alt="A catalytic converter cut open: two ceramic honeycomb blocks of parallel channels between a sensor ahead and the oxygen sensor behind, with a close-up of the rough coating that carries platinum, palladium and rhodium." width="1251" height="672"></a> <p>Diagram: <a href="https://oilandmiles.com/articles/what-is-a-catalytic-converter">Oil & Miles</a>, CC BY 4.0</p>Why are catalytic converters so expensive?
Because of the metals painted inside, and those prices move on their own, with nothing about your car changing. Rhodium, the most expensive, fell by more than three quarters between 2021 and 2024.
A converter holds a few grams of these metals rather than ounces, so none of the metal prices is what you'll pay. A replacement built to federal emissions rules runs $402–$1,846, parts and labor, on the cars in our replacement cost guide.
Metal prices explain why the same part carries a different price each year while the car it fits stays the same. The United States imports most of its platinum and palladium, so production abroad moves those prices too.
Why do catalytic converters get stolen?
Because the coating is recovered and resold by the ton, and that puts a cash value on a part a thief can cut off a parked car. The same metals make the replacement expensive, which is why a theft hurts so much.
Our theft prevention guide covers what slows a thief down. If one has already gone, ask your insurer whether your policy covers it before you pay for the part.
How long does a catalytic converter last and what kills it?
There's no set life, because it has no moving parts, and left alone by a healthy engine it can last for many years. What kills one early is liquid or heat it wasn't designed for, and once the honeycomb has melted, broken up or filled in, it's finished.
So four things get a catalytic converter killed or blamed, and the first three cost less to fix than the converter, which is why the order of repairs matters:
1. A misfire
Raw fuel from a misfire burns inside the converter rather than in the cylinder, and the heat can melt the channels shut. A flashing check engine light is the warning that this is happening now.
Have the misfire fixed before you pay for a new converter. Otherwise the new one meets the same fuel the old one did.
2. A wrong fuel mixture
An engine that keeps running rich, with too much fuel, or lean, with too little, overheats the catalyst. That's why the engine computer uses the oxygen sensors to hold the mixture so tightly in the first place.
So fix the mixture first, with the codes and the oxygen sensor readings as the guide. A new converter on an engine that still runs rich or lean overheats the same way.
3. An exhaust leak
Walker, a converter maker, lists exhaust leaks among the main reasons the gases reaching a converter go wrong, and correcting them is a step in its diagnosis. The converter itself can be fine.
That makes a leak the cheapest thing you can rule out before anyone condemns the converter. It's the first thing to ask a shop about.
4. Coolant or oil
Coolant from a failing head gasket coats the metals and stops them working, and oil an engine is burning does the same. With coolant, white smoke from the tailpipe often comes first.
Walker names coolant leaks as a cause and tells installers to examine the cooling system. Have the leak or the oil burning fixed first, or a new converter gets coated the same way.
What are the two ways a converter fails?
It stops converting or it stops flowing. The first you can't feel, and it sets a code such as P0420. The second you feel as a car that won't pull, and the two share a name and almost nothing else.
| The failure | What you notice | What has happened |
|---|---|---|
| It stops converting | No driving symptom at all | Honeycomb intact, the chemistry is gone |
| It stops flowing | Lost power, a struggle to rev | Honeycomb broken up, melted or filled in |
| Both at once | The usual end state | A melted one stopped converting too |
Only the second changes how the car drives, so a converter that sets a code but drives normally hasn't blocked. Our guide to bad catalytic converter symptoms covers what each one looks like.
A melted inlet
Muffler vs catalytic converter: what's the difference?
Two cans in the same pipe doing two unrelated jobs. The converter cleans the gas and the muffler quiets it, and four differences separate a muffler from a catalytic converter.
| What differs | Catalytic converter | Muffler |
|---|---|---|
| Its job | Changes what is in the gas | Makes it quieter |
| Where it sits | Near the engine, for the heat | At the back |
| The law | Illegal to bypass, 8-year or 80,000-mile warranty | Neither rule applies |
| When it fails | Silent, usually code P0420 | Loud, no code |
A converter that has broken up rattles, though, and that one can sound like a muffler until somebody looks. The prices aren't in the same class, because the converter is the one carrying rhodium.
A resonator is a third can, doing the muffler's kind of work on particular frequencies. Like the muffler, it leaves the gas just as it found it.
Where is the catalytic converter and how many does a car have?
Under the car, close behind the engine, and often more than one. The first converter sits at or inside the exhaust manifold, the pipe that collects the gas from each cylinder, on many cars, because it needs the engine's heat to work.
A four-cylinder can have one or two, and a V6 or V8 usually has at least one per side, because each side of the engine has its own exhaust manifold. Those sides are called banks, which is why a code can name bank 1 or bank 2.
Use this image
Free to republish under CC BY 4.0: credit Oil & Miles and link to this page. The snippet does both.
<a href="https://oilandmiles.com/articles/what-is-a-catalytic-converter"><img src="https://oilandmiles.com/assets/img/diagrams/what-is-a-catalytic-converter-underside-r3.svg" alt="What is a catalytic converter, where it sits: a four-cylinder engine seen from under the car, front at the left, drawn see-through, with the first converter at or inside the exhaust manifold, a rear one under the floor, and the downstream sensor just after the first converter, shown in an inset." width="1170" height="800"></a> <p>Diagram: <a href="https://oilandmiles.com/articles/what-is-a-catalytic-converter">Oil & Miles</a>, CC BY 4.0</p>Is it illegal to remove a catalytic converter?
Yes, under federal law, and not as a gray area. Taking a converter off, hollowing one out or fitting a straight pipe in its place: none of these is permitted.
The Clean Air Act makes it illegal to sell or fit any part whose main effect is to bypass or disable emission equipment. That covers whoever sells the part as well as whoever fits it.
Fitting a new one has limits too. A cheaper aftermarket converter is allowed only in three cases: the old one is missing, it has failed an inspection, or the car is past 8 years or 80,000 miles with a documented need. So a working converter can't be swapped for a cheaper one.
Outside the US
These limits are US federal law. In the UK, a converter that is missing, obviously modified or obviously defective fails the MOT as a Major defect on cars first used from September 1, 2002, under section 8.2.1.1 of the GOV.UK MOT inspection manual.
What should you check before replacing a catalytic converter?
Check who might pay and what's feeding it before anyone replaces it. To read a catalytic converter quote, start by asking what it is made of:
- Ask what the quote is made of. A new aftermarket converter must carry a 5 year or 50,000 mile warranty on the shell and pipes. A used one must be tested and labeled instead. In California, a replacement must be one its Air Resources Board (CARB) has approved, sold as California grade, and a used one isn't allowed.
- Check the age and mileage first. Under 8 years and 80,000 miles on a 1995 or newer car, the converter is a major emission control component and the federal emissions warranty may still cover it.
- Ask a dealer about recalls on your VIN. Our free VIN decoder lists your model year's recalls before you go, and NHTSA's VIN search shows which are still open. Ford, GM, Kia and the Chrysler group have converter recalls or special coverage on some models, one of them for 15 years. Our catalytic converter replacement cost page lists them.
- Fix what is feeding it. That means the misfire, rich mixture or coolant leak, before the new part goes in.
If a step hits a dead end, because no program covers your VIN or the quote won't say what's in it, here's where to go next:
- No recall or coverage on your VIN. The federal 8-year, 80,000-mile warranty is the next check. States that follow California's rules cover some cars longer, so read your warranty booklet before you pay.
- The quote doesn't say new, used or California grade. Ask which before you compare it.
From the documents
What do the rules and the metal records say?
The federal warranty covers a converter for 8 years or 80,000 miles, and EPA allows an aftermarket one in only three situations: missing, failed an inspection, or past that warranty with a documented need. The metal figures behind this page come from USGS.
Regulation 40 CFR 85.2103(d)(1)
[T]he following specified major emission control components have a warranty period of eight years or 80,000 miles: (i) Catalytic converters and SCR catalysts, and related components.
Aftermarket converter policy Question 6
Generally, there are only 3 situations when you can install an aftermarket converter. [...]
Aftermarket converter policy Opening
[A]ll persons engaged in the business of automotive service and repair [...] are prohibited from installing or selling aftermarket catalytic converters which have not met the criteria of EPA's interim enforcement policy [...].
Mineral Commodity Summaries Platinum-group metals, February 2026
The leading domestic use for PGMs was in catalytic converters to decrease harmful emissions from automobiles.
- Metal per converter. A few grams, varying by car: 3–7 of platinum, 2–7 of palladium and 1–2 of rhodium (Road & Track, citing Waste Advantage Magazine), or 0.1–2 of rhodium (Ledoux, an assay lab).
- Metal recovered. About 50,000 kilograms of palladium and 8,600 of platinum came back out of US car converters in 2025, USGS estimates, of roughly 140,000 kilograms of the two recycled worldwide.
- Supply. In 2025 the US relied on imports for an estimated 89% of its platinum and 57% of its palladium, and one company in Montana does all of the country's platinum-group mining. Production in South Africa, the leading producer, fell an estimated 9% in 2025.
- Diesel converters. USGS says around 25% of the platinum in a diesel converter can routinely be swapped for palladium, sometimes as much as 50%.
- How it changed. EPA's account says early converters were oxidation converters only, dealing with hydrocarbons and carbon monoxide and containing platinum, palladium or both. In 1980 or 1981, earlier on some California vehicles, makers began fitting converters that also reduced nitrogen oxides, which needed rhodium, computer control and oxygen sensors.
- Working temperature. Walker, a converter maker, puts it at 500 to 800°F, rising to 1,200°F under heavy load.
- New aftermarket warranty. EPA's policy asks for 5 years or 50,000 miles on the shell and pipes and 25,000 miles of emission performance.
- Converters per car. The 2010 Honda Accord 2.4L has two, a front one inside the exhaust manifold and a rear one under the floor. The 2012 Ford Focus 2.0L has two, one at the manifold and one further back, the 2012 Ford F-150 5.0L V8 has two, one per bank, and the 2014 Honda Odyssey 3.5L V6 has three, two small ones at the front manifolds and one at the rear. Nissan sells the 2013 Altima 2.5L's front converter as one assembly with the manifold, and the catalog doesn't give a total count.
- Rhodium prices. By USGS estimates, rhodium peaked in 2021, lost more than three quarters of that by 2024 and rose a little in 2025.
Conclusion
What to do next about your catalytic converter
Check who might pay and fix what is feeding the old one before you pay for a new one. Don't remove it or hollow it out, since federal law forbids both.
When a quote looks high, look at the metals before you blame the shop. Oil & Miles checks these facts against federal rules and published metal prices, across owner guides.
Common questions
Asked most often
Is a catalytic converter covered by warranty?
On a 1995 or newer car, the federal emissions warranty covers it for 8 years or 80,000 miles as a major emission control part. Past either, the repair is yours unless a recall or a carmaker's coverage applies.
What is inside a catalytic converter?
A ceramic block extruded into thousands of parallel channels, coated with a rough layer, the washcoat, that carries platinum, palladium and rhodium. The channels give the exhaust an enormous surface to touch as it passes through.
Can a car run without a catalytic converter?
Mechanically yes, legally no. Section 203 of the Clean Air Act prohibits selling or installing a part whose main effect is to defeat an emission control device, and a missing converter fails an emissions test in the states that run one.
What is the difference between a two-way and a three-way converter?
A two-way, or oxidation, converter handles carbon monoxide and unburned fuel only, and that was the early generation. A three-way adds nitrogen oxides, which needs rhodium and needs the oxygen sensors and computer control that arrived with it around 1980.
Does a catalytic converter reduce power?
A working one costs a little back pressure, and the engine is designed around it. A blocked one is a different matter and shows up as a car that won't pull.
What people ask next
Sources
- USGS Mineral Commodity Summaries, February 2026, platinum-group metals, read at source, for every price here, the recovery figures for converters scrapped in the United States, and the import reliance percentages. US Geological Survey, read October 3, 2026
- EPA, What You Should Know About Using, Installing, or Buying Aftermarket Catalytic Converters, read at source, for the history of oxidation and three-way converters, the three conditions for fitting an aftermarket one, the warranty requirements, and the Section 203 prohibition. US Environmental Protection Agency, read August 26 and September 16, 2026
- 40 CFR 85.2103, the federal emission warranty, read at source, for the 8 year or 80,000 mile coverage that applies to a catalytic converter as a major emission control component. Cornell Legal Information Institute, read August 26, 2026
- RockAuto and dealer parts catalogs, for how many converters the 2010 Honda Accord, 2013 Nissan Altima, 2012 Ford Focus and F-150 and 2014 Honda Odyssey carry and where each sits. RockAuto, HondaPartsNow, NissanPartsDeal, read September 4, 2026
- Walker Exhaust Systems, its Catalytic Converter FAQ, for the converter's normal and heavy-load working temperatures. walkerexhaust.com, read August 25 and re-read September 16, 2026
- Road & Track and Ledoux & Company, for the trade figures on grams per converter. Road & Track and Ledoux, read November 1, 2026
- Stanford Q&A on how converters go bad, for the catalyst losing strength with age. Stanford University, read November 1, 2026
- California Air Resources Board, aftermarket converters, for the used-converter ban. CARB, read November 1, 2026
- Walker technical pages, a converter maker, for exhaust leaks and the cooling-system check before a new converter goes in. Tenneco (Walker), read October 2, 2026
- MOT inspection manual, section 8.2.1.1 (exhaust emission control equipment), for the UK MOT result on a missing or defective converter. GOV.UK, read November 4, 2026
AI illustration by Oil & Miles
How this was compiled
The article is built around the metals, because they explain why the part costs what it costs and why the figure moves. How converters changed around 1980 comes from EPA's own description, which also explains why oxygen sensors arrived at the same time. Metal prices are USGS estimates for 2025 and averages for earlier years.
What we didn't do
We didn't weigh the precious metal content of any converter. The gram figures in the record are trade sources', not ours, and loadings vary by engine, by market and by year.
We give no scrap value for a converter. That market prices individual part numbers, it moves weekly, and publishing a figure would be closer to a shopping guide for thieves than to anything a car owner needs. We didn't compile state emissions test rules either, because they vary and aren't federal.
Metal prices are USGS annual averages, and a real US bill varies by region, engine and shop rate. Prices from $10 up are rounded to the nearest dollar, so $14.13 reads as $14 and $14.52 as $15. Below $10 they're exact. This article is general information, not advice about your specific vehicle. See the disclaimer.