Depending on manufacture year [MY], different strategies can be applied. Smog Check is the standardized test to make sure the emission system in your vehicle is working properly. For year 2000 or newer, you need to verify the On Board Diagnostic [OBD] system is functioning properly and without any recorded codes. For MY 1996 – 1999, not only OBD must function properly, vehicle must also passes the dyno-test. Also fuel cap is tested for leak. For MY 1995 and older, in additional to OBD [if equipped], dyno-test and fuel cap test, the evaporative system will be tested for leak. Above information apply to most vehicles with the manufacture year described. For commercial trucks, test can be varied depending on the weight of the vehicle. There are exceptions that will not be discussed here. Consult www.smogcheck.ca.gov for more information. If you doubt that your vehicle may not pass smog check, you can opt for a pre-test.
To locate a Smog Check Test/Repair station for a complete diagnosis on smog check failure. List of Test/Repair stations are list in Bureau of Automotive Repair [BAR] website or visit www.smogcheck.ca.gov to find out details. The strategies are to diagnose the smog check failure, to obtain a written itemized estimate, to repair the emission defect, to perform a pretest to verify the repair, and to retest vehicle. All diagnosis and repairs of smog check failure should be performed by a BAR certified Smog Check Test/Repair station.
Best source of information is found in owner's manual of your vehicle. Owner manual also list other vital fluid requirement and capacity recommended by the manufacturer such as transmission fluid, coolant, brake fluid etc. In general, regular [non synthetic] motor oil and oil filter should be changed around 3000 to 5000 miles, depending on the operating condition and other factors that degrade motor oil. Synthetic oil typically last longer than non-synthetic. Consult owner's manual for correct information.
In essence, the difference is the size of the oil molecules. Full or 100% synthetic oil has mostly uniform oil molecules. Regular oil has non-uniform oil molecules. Blend synthetic is the combination of regular and full synthetic. Uniform oil molecules help engine internal parts to move smoother than non-uniform ones. Note that the ratio of blend synthetic oil can vary from 1% full synthetic/99% regular to 99% full synthetic/1% regular. It's to the discretion of the vehicle owners to find out what they are buying in blend synthetic motor oil.