Why might older vehicles fail emissions tests?

Older vehicles are likely to fail emissions tests primarily due to the deterioration of emissions control components as they age. Over time, critical parts such as catalytic converters, oxygen sensors, and other emission control devices can wear out or become inefficient. This degradation can lead to increased emissions of harmful pollutants, making it difficult for the vehicle to meet the stringent standards set for modern emissions.

The design and technology used in emissions control systems have improved in newer models, where these components are generally more reliable. In contrast, older vehicles may not have the same capabilities or functionality, leading to a higher likelihood of failing the emissions test as components become less effective.

While other factors, such as maintenance history or types of fuel used, can impact emissions, it is primarily the age-related wear and tear on emissions control systems that poses the most significant risk for older vehicles failing emissions tests.