Getting an oil change before a smog inspection is not required, but may help your Suburban pass the smog check if it has not had an oil change past its oil change maintenance due date.
The PCV (positive crank ventilation) system of your Chevy Suburban allows the engine to breath fumes from engine oil compartments such as the oil pan and all chambers where oil is present. Contaminated oils (oil which is not changed past 5000-10000 miles, depending on the type of oil used) are high in Hydrocarbons (HC) and will cause a rich fuel mixture when the PCV combines the fumes with fresh air; in the intake manifold.
If the oil in your engine is contaminated due to inadequate oil changes it may cause your Chevy Suburban to fail the inspection.
