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Growing concern over clean air has spurred state governments to impose vehicle emission checks. Some states require mandatory emissions testing, while others don't require them at all. Star Smog Depot offers STAR Certified smog tests for all vehicles in Colma, Daly City, and the surrounding Bay Area cities. Our experienced technicians perform smog checks only, but can also provide advice on how to reduce your emissions. We look forward to working on your vehicle! See below for a list of smog test we can do.

All DMV Required Smog Tests  •  Diesel Smog Tests  •  Gold Shield Directed Smog Tests  •  Gross Polluter Certification  •  Out of State Smog Tests  •  Smog Test Certifications  •  STAR Directed Smog Tests

*Free Retest Applies to 2000 and Newer Passenger Vehicles

star certified smog test station, star certified smog check station


  • Your check engine light should be OFF.
    A lit check engine light will cause you to automatically fail your smog test. A certified smog test shop can use a trouble code retrieval tool to extract trouble code data from the ECU. Star Smog Depot can recommend auto repair shops to turn the check engine light off.
  • Inflate your tires.
    If your vehicle is 1999 or older it will be driven on a dynomometer while a sample of its exhaust is collected by the smog machine. Ensuring your vehicle's tire pressures are even and correct will help you pass the smog test. This will greatly improve your chances of passing the smog test by allowing the engine to maintain a constant and steady load. Accurate tire pressure (as required by the tire and vehicle manufacturer) may be the deciding factor between a borderline vehicle passing or not passing the emissions test. 2000 and newer vehicles are not administered the exhaust emissions portion of the smog test.
  • If you haven't had an oil change within the last 5,000 miles, do it before the smog test. "
    If the oil in your engine is contaminated due to inadequate oil changes it may very well cause your vehicle to fail the smog check. Not performing regularly required oil and filter changes not only causes premature engine wear but can also cause your vehicle to not pass the smog inspection.
  • Drive your vehicle for at least 20 minutes prior to arriving at Star Smog Depot.
    This will ensure your coolant, oil, and catalytic converter reach and maintain optimum operating temperature. To ensure a passing smog test and adequate combustion, it needs to have sufficient time to warm-up and this can be accomplished through driving for at least 10 to 15 miles. Emission test standards require a smog check technician to ensure a vehicle is at proper operating temperatures prior to administering the smog test.
  • Use fuel additives which can be helpful in lowering emission levels.
    Fuel additives are generally poured into a vehicle's gas tank during fuel refueling. The additive is mixed with your vehicle's fuel to clean carbon deposits within your engine's intake and exhaust paths, allowing for both fuel and air to flow freely within its passages, thus lowering emission levels, improving combustion, increasing overall engine performance, and helping you pass the smog test. Note: Fuel system additives and fuel system treatments require using the complete application and refueling with fresh fuel prior to the smog check. Read your fuel additive's instructions regarding having your vehicle smog tested while using the additive.
  • Avoid wet/rainy weather.
    Your vehicle (assuming it's registered in one of the larger counties in California and is model year 1999 or older) will need to be driven on a dynamometer during the emissions test. If wet, your car's tires will be slipping and losing traction as the smog technician tries to maintain required test speeds. Unstable engine and drivetrain torque is not the best conditioning your vehicle should receive if you plan on getting passing smog test results. This is not to say you can't get a passing smog test on a rainy day. The smog machine has a "dry tires" mode, which will dry your vehicle's tires before the test. However as we mentioned, you don't want to place any extra strain on the engine before or during the smog test.
  • Has your vehicle's battery been disconnected, replaced, or jump started recently?"
    We recommend holding off on getting the smog check for at least one week while you drive your vehicle regularly. Chances are while your vehicle's computer lost power, its internal self test monitors were erased. Without these important and required emission monitors your vehicle can not pass the smog test. You will be required to drive between 100-200 miles and over the course of a week in order to reset or "complete" the emission monitors.
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