Keeping the environment clean and free from pollution is our duty as inhabitants of the earth.

One way we can contribute to this is by using environmentally friendly products in our daily lives. After all, the earth is our home and we must protect it from harm. The main factor that damages our environment is harmful gases.

These gases are released from various places such as factories, ships, animals, and vehicles. There is not much we can do to influence large companies and industries, but we can do our part by keeping our vehicles emission-free.

As such, emission tests or smog tests have been developed by governments around the world with environmental health in mind. But what does a smog test involve? Let’s find out.

What Does A Smog Test Entail?

A smog test determines the number of harmful emissions your car emits into the air. Every engine emits emissions, but you can control how much of it escapes into the environment. To this end, scientists and engineers have made some advances in technology to minimize emissions. One of these technologies is the catalytic converter.

This small engine component filters a vehicle’s exhaust gases and makes them less harmful before they are released into the air. There are other ways of reducing emissions, but we will come back to that later. Let’s concentrate first on what happens during a smog test.

Smog tests used to be quite complicated. You had to take your vehicle to a facility where it was placed on the dynamo and the test equipment was attached to the car’s exhaust pipe. Now, modern solutions are available, and all the technicians have to do is connect your car to an OBD2 scanner and extract all relevant information. A visual inspection is also carried out.

This depends on which country you live in. In some countries, you are not required to carry out a smog test for your vehicle.

Each vehicle has a specific rating. This rating is provided by the government and your vehicle must meet it every few years. If you do not meet the requirements, there could be consequences.

How to Pass an Emissions Test

We understand; you have to pass the emissions test to keep your car on the road. If you fail the test, you will have to pay a fine, which can be quite high by modern standards, which can lead to you being unable to make expensive repairs if you fail the test. Here is what you can do to increase your chances of passing a smog test:

1. Get Rid of the “Check Engine” Light

Exhaust Smog Check

The Check Engine light indicates that there is something wrong with your car and that it is not working efficiently. If your car has the check engine light on the dashboard, you will certainly not pass the test. Get a correct diagnosis of your car before the test to improve your chances.

One reason why the check engine light illuminates is a defect in the oxygen sensor. The oxygen sensor measures the quality of the exhaust gases leaving your vehicle. It must work in perfect condition to pass the smog test. An oxygen sensor is a cheap part and can be replaced for $170. A small price considering the amount of penalty you would have to pay.

2. Drive the Car at Highway Speeds Before the Test

When you drive your car at high speeds, the catalytic converter heats up, burning all the fuel and oil residue in the exhaust system. Perform this exercise at least two to three weeks before the test. And also try to drive quickly on the way to the test center to completely clean the catalyst of any residue.

The worst thing you could do is drive slow and clog up the catalytic converter.

3. Refill/Replace the Engine Oil

Check when you last changed the oil. If your refill date is near, have your oil changed. It is important that you have the smog test done with fresh oil in your engine. Used and spoiled engine oil will produce additional harmful gases that could cause you to fail the test. Try not to be overdue for an oil change and always buy a high-quality oil filter.

4. Tune Your Vehicle Prior to the Test

Tune your vehicle two weeks before the exhaust emission test. Do not tune it close to the test date, as the ECU resets itself after tuning and it will not be able to make the correct diagnosis necessary for a correct recommendation.

5. Add fuel additive

There are several great fuel additives that are manufactured to improve for better emissions in your car. You can check this one out here on Amazon, which worked really well on the cars we tested.

6. Check All the Fluids Before-Hand

To maintain high speeds, your car must be properly hydrated. When tested on a dynamo, there is a possibility that your car will heat up, and if the radiator does not contain enough coolant to cool the engine, the engine could produce a rich air-fuel mixture, which could affect your emission levels.

7. Get a Mock Inspection

In some states, you can have a mock inspection carried out for a small fee. This inspection will give you a good idea of your chances in the actual inspection. If the test shows that you have failed, you can make the right adjustments to get below the limit. This way, nothing is officially recorded and you get a good analysis.


Make it a habit to take care of your car regularly. If you are careful, you will never have to worry about passing a smog test.