Few tips how to improve emission test results

This section used in it's entirety comes from a longer articles and comes from samarins.com

- Change oil before testing. For old or high mileage car using a thicker oil may help.
- Change spark plugs and air filter if it was a while ago since you've changed them last time. Complete tune-up may be an option for older cars.
- Flushing the fuel injectors usually helps.
Before the test:
- Check and adjust tire pressure
- Fill the car with premium gas
- Take a car for a spin on a freeway - it helps to clean spark plugs and catalytic converter.
- Make sure, the engine is fully warmed up before test.

If you have check engine light on, exhaust leaks, broken gas cap, or any other problem with vehicle emission system it needs to be repaired before the test - all those items will be inspected during the emission test.