How to pass a smog test

How to pass a smog test

An important aspect of owning and maintaining a vehicle is ensuring that it complies with State emissions laws. Smog tests were introduced in the 1970s along with amendments to the Clean Air Act, the aim of the tests is to reduce the levels of air pollutants. A lot of drivers push the smog test to the back of their minds, preferring to deal with the consequences when the time comes. However, the inconvenience of the smog test pales in comparison to the consequence of failure and subsequent repair bill.

With some forethought and preparation the chances that your vehicle will pass the smog test on the first attempt increase greatly. You will find our tips and recommendations on how to pass a smog test below.

Our advice and recommendations fall into two categories, what you can do to prepare and what our certified technicians can do to help you pass.

In the lead up to your smog test we highly recommend that you schedule a vehicle inspection, this will help you and us identify any potential issues which could cause you to fail, such as:

  • Check engine light. If the check engine light is illuminated at the time of the smog test your vehicle will automatically fail. To avoid this book your vehicle in for a diagnostic service, this will allow our technicians to identify and fix the issue;
  • Check the coolant level. Your vehicle will be tested indoors so there won’t be air being drawn through the engine to cool it. You can either have one of the technicians check the coolant level or check it yourself by following one of our previous guides [insert hyperlink to coolant/antifreeze how to]. Ensuring that there is enough coolant in the radiator will help prevent your engine from overheating;
  • Oil change. Our technicians can check the condition of your engine oil and can perform a flush of the system and change the oil if needed;
  • Tire pressure. Overly inflated or underinflated tires can have a drastic impact on your vehicles fuel efficiency as well as the outcome of the smog test. Let our technicians make sure that your tire pressure is just right;
  • Tune up service. Depending on the results of your vehicle inspection, a tune-up service may be recommended to you. When such a service is booked, our technicians will perform any needed repairs or replacement of parts to ensure your vehicle runs at its full potential.

With your vehicle is running at its best again you have one less thing to worry about, at this stage your vehicle stands a good chance of passing the smog test on the first attempt. However, there is more you can do to increase your chances.

  • Drive fast. For the two weeks leading up to your smog test, we recommend that you, safely, drive as close to the speed limit as possible for around 150-200 miles. Your engine likely contains a catalytic converter, this engine part is responsible for converting harmful pollutants into less harmful emissions. However, regular daily use of your vehicle doesn’t give the catalytic converter much of a chance to reach the temperatures necessary for it to do its job properly. Pushing your vehicle to travel at higher speeds prior to the test will allow the catalytic converter to clear out any built-up residue and perform as it should;
  • Gasoline. On the day of your smog test you should make sure that your gas tank is at least half-full, however, a full tank is recommended. During some smog tests, a vehicle is placed on the dynamometer at an angle which can expose the fuel pump. If there is not enough fuel in the tank it will cause there to be more vapor in the fuel line, this can lead to failing the test.
  • So there we have it, your quick guide on how to pass a smog test. Did we miss anything or do you have any tips or advice about passing a smog test? Let us and for our readers know, we are always happy to hear from you!


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  4. I took this test on my car. But it would be interesting to rent suv pass the test?


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