What factor can affect a vehicle's emissions system performance?

The performance of a vehicle's emissions system is significantly influenced by the type of fuel used. Different types of fuel have varying chemical compositions, which can directly impact the combustion process and the resulting emissions. For instance, fuels with higher octane ratings can promote more complete combustion, reducing harmful emissions. Additionally, fuels containing high amounts of sulfur or other contaminants can lead to increased emissions and potential damage to components of the emissions control system, such as catalytic converters.

While factors like the vehicle's color, tire size, and how often the vehicle is washed might affect the vehicle's overall performance or aesthetics, they do not have a direct relationship with the functioning of the emissions system. Consequently, these elements are not critical factors in determining emissions performance, thereby emphasizing the importance of fuel type in regulating emissions.