What is a Smog Check? (& How to Pass It)

Vehicles are a big part of the pollution of our earth and therefore many countries and states are doing a yearly test to make sure your vehicle is not spitting out bad exhausts. Here's what you need to know about it.

What Is A Smog Check

A vital automotive inspection done in many states is the smog check. These checks evaluate how much pollution your car is putting into the atmosphere based on the emissions. While each state has different requirements, the basic concepts remain the same. 

In this article, we will define the smog check, look at the pricing and give you some tips that should help you pass the test. Not only will this guide ensure you are following the rules, but it can also help you avoid a smog test failure.  

What is a Smog Check?

While the term smog check has become popular in California, many other states have similar emission laws.

A smog check or smog test is a basic vehicle inspection program that measures how many pollutants are coming from a car’s exhaust. In some cases, the smog check involves a physical inspection, while others will read the onboard computer for faults.

Many emissions tests also include reading the exhaust coming out of the tailpipe.

How Much is a Smog Check?

In California, the smog stations are private businesses that were authorized by the DMV. In this state, prices can vary greatly, with prices ranging from $30 to $80. However, other states have different price scales, depending on what the test looks like and what the requirements are.

Some states combine the emissions test with the regular inspection, creating a bundled price. While you might spend more on the inspection, you must remember that the total price isn’t all for the emissions check. 

How to Pass a Smog Test

1. Warm up the Car Engine

Smog Test

Inside the car engine, fuel is burning. If you want combustion to operate at its best, the engine needs to be completely warmed up. 

The warmer the engine is, the fewer amounts of hydrocarbons are going to come out of the tailpipe. To perform even better, consider taking the vehicle in on a cooler day. With cool air coming into the engine when it is fully warmed up, the motor will run most efficiently. 

In general, your engine should run at least twenty minutes for it to be fully warmed up. Maybe you should choose a station that is this far from your home. 

You also won’t want to wait long for your appointment or the engine could cool down. Choose a station with short lines. 

2. Use a High-Quality Fuel Additive

Fuel additives are simple to use and can help your engine run more efficiently. Simply pour an additive into the gas tank when you fill-up. 

These fuel additives remove carbon deposits from the engine, making the exhaust cleaner. With a cleaner system, the air and fuel can flow easier, lowering the emission levels while improving combustion efficiency. 

CRC is one brand that creates an additive guaranteed to pass emission tests or you get double your money back. It does cost a little more, but it’s better than paying for multiple smog tests. 

RELATED: 8 Best Catalytic Converter Cleaners & Additives

3. Inflate Your Car Tires

In some areas, the technician drives your vehicle using a dynamometer. To encourage a passing grade, you want to fill your tires to the highest end of the normal range for this test. 

For example, if your tire manufacturer recommends an inflation range of 32 to 44 PSI, inflate them to as close to 44 as you can get. Don’t exceed this amount, but take it as high as what is safe.

With higher air pressure in the tire, the engine has to work less to turn the wheels. If the engine isn’t working hard, the emissions should be cleaner. 

4. Change Your Oil

In the engine, there is a positive crank ventilation (PCV) system. The purpose of this system is to recycle the fumes in the engine compartment for further burning. 

However, if the motor oil becomes contaminated because you haven’t changed it, you could hinder the process, thereby leading to higher emissions. That’s why we always recommend changing the oil and filter right before a smog test. 

5. Turn off the Check Engine Light

Depending on the type of test you are taking, having the Check Engine Light on will result in an immediate failure. If you have this warning light on the dash, you should use your OBDII scanner to find the problem. You can also get a free check at most auto parts stores. 

Repair the issue and have the codes reset, so the light turns off. If you can only get the light to turn off for a short time, make sure you get to the smog check test station promptly. 

6. Choose a Station with a Free Retest

If you are struggling to pass the vehicle smog test, you want to find a station providing free retests. In some regions, the competition among these providers is fierce, so you shouldn’t have trouble finding one. 

With this added insurance policy, you won’t have to worry about failing. You can try some of our steps and retest without paying more money. 

Hopefully, you won’t need to retest, especially if you follow our tips. Thankfully, once you pass, you don’t normally need another check for a year. 

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Written by:

Magnus is the owner and main author of MechanicBase. He has been working as a mechanic for over 10 years, and the majority of them specialized in advanced diagnostics and troubleshooting. Certified Automotive Diagnostic Technician.