Can you drive a car without a catalytic converter?

A catalytic converter, also known as a catalyst, is a part of the car’s exhaust system specially made to reduce the pollution and toxic elements from the air-fuel mixture combustion.

You can still drive without a catalytic converter, but the car will have increased emission of harmful gases, be non-compliant with environmental standards, bad smell because of gases in the interior, increased noise from the car, and the likelihood of exhaust system failure.

car catalyst

The catalyst is monitored by one or two oxygen sensors or lambda probes, based on the signals from which the ECU (Electronic Control Unit) adjusts the proportions of the air-fuel mixture. In general, its role is to try to make the environment less polluting.

Read more about the role of the catalytic converter

Why do drivers want to remove the catalytic converter?

Removing the catalytic converter is not a legal procedure in most countries. This consists of cutting out the part completely or knocking out its filling. This is done for several reasons, but the result is always the same, the car emits exhaust gases into the atmosphere without any reduction in toxicity. 

It is also believed that the removal of the catalyst can reduce fuel and engine oil consumption, and also increase engine power, but this is not true. It is not a good and cheap form of tuning.

Under ideal conditions, the catalytic converter is fully capable of working 120.000 to 170.000 kilometers, or 74.000 to 100.000 miles. After that, problems will begin. In particular, the engine power will decrease, the fuel consumption will gradually increase, the idle speed may float, and so on.

Most of the time, drivers think that removing the catalytic converter will increase engine power or reduce fuel consumption. In fact, almost no one even remembers this element of the exhaust system as long as it works properly. However, like any other part, a catalytic converter will fail at some point.

Another common reason why drivers want to remove the catalytic converter is its wear. When it is failing, it gets clogged and needs to be replaced, but a new catalytic converter is very expensive because of the precious metals it contains, platinum, rhodium, and palladium.

In this case, resorting to searching for a used catalyst from a car junkyard is not advisable. As well as buying an aftermarket one or a cheap fake instead of the original.

The advantages and disadvantages of removing the catalytic converter

1. You save money by not replacing the old catalytic converter with a new one

This seems like the only advantage if we talk about the pros and cons of removing the catalyst. As I mentioned above, the original part costs a lot of money. And given the uselessness of the catalyst in terms of the car’s dynamic characteristics, its replacement naturally raises doubts among many.

Just removing the catalytic converter without other actions, and expenses, will not work. You will have to, at a minimum, insert a replacement in its place. 

Also, it will be necessary to adjust the ECU’s software so that it “doesn’t notice” the loss. And the procedure itself, if you did not dare to do it yourself, costs some money. In general, costs cannot be avoided, you can only make them lower.

2. Fuel consumption

A clogged catalytic converter makes the car consume more fuel, so the owner wants to remove it thinking that fuel consumption will return to normal values, moreover, it will even decrease.

If he has the chance to go to an unreliable car repair shop, the mechanics there will feed him the false impression that after removing the catalyst, the car will consume even 30% less.

In reality, however, opinions are divided, some say they have not noticed better fuel consumption, and others have said that consumption has actually increased.

In practice, after the catalytic converter was removed, other operations were performed which involve, in particular, software changes for the ECU. But after that, the reduction in fuel consumption was almost imperceptible in the long run.

3. Engine power

Everything is the same here as with fuel consumption. It is impossible to say with absolute certainty that after removal, the engine power will increase. Therefore, engine power can not be ranked among the pluses of removing the catalytic converter. 

4. Engine oil

I heard a lot of automotive enthusiasts say that removing the catalyst would help reduce engine oil consumption. Nothing more false. The catalytic converter or its removal has nothing related to engine oil consumption.

Yes, exhaust capacity indirectly affects engine oil consumption. But it is so insignificant that it is silly to hope for noticeable improvements only after cutting the catalytic converter.

5. Exhaust noise

This is one of the big disadvantages when driving without a catalytic converter. The noise level of the exhaust system will significantly increase. Hot and fast-moving exhaust gas resonates in the empty catalyst bank. If the car has weak noise insulation, then this noise will annoy you in the cabin while driving.

To return to the initial state, you will need to install a new catalytic converter.

6. Bad smell

Another common disadvantage when driving without a catalyst is a bad odor inside the car, there is a high concentration of carbon monoxide at a higher temperature than expected, and other smelly impurities that burn out and decompose in the working catalyst.

When this part is removed, you will feel all the smelly gases inside the car.

7. The car pollutes more

This is the biggest disadvantage when you are driving with an absent catalytic converter. Of course, for many, this disadvantage is not significant, because they don’t care at all, especially against the background of high prices for new catalysts. 

The loss of a big sum of money is more noticeable and more real than polluting the environment, which everyone talks about, but few people see.

8. Failing the periodical inspection

In most places, the car runs into a periodical inspection to check if the car is in a good technical condition to drive on public roads. The inspection period differs, can be once every 3 or 6 months, once a year, or on newer cars, once every 2-3 years.

Because you removed this part, you will certainly fail this inspection and the car will no longer have the right to be driven unless you do so at your own risk.

It is illegal to drive without a catalytic converter?

In most countries yes, it is illegal to remove the catalytic converter and to drive the car without it, because it is prohibited by law to change the factory design of the car’s exhaust system. If you get caught, you will risk big fines, including car confiscation.


Removing the catalytic converter doesn’t do anything beneficial for your car, on the contrary, driving without it can be annoying and will do more harm to the environment.

The bad news is that catalytic converters thefts have intensified lately, because they sell very quickly and at extremely good prices, even if they are used.

The most exposed cars to such thefts are the older ones that have this part under the car, and it is easier to remove it. And this aspect will mean a lot of headaches for the victim.

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