What is a common outcome when vehicle windows are not properly secured?

When vehicle windows are not properly secured, one common outcome is moisture intrusion. This refers to the unwanted entry of water into the vehicle's interior, which can occur during rain or in humid conditions. If windows are not closed tightly, gaps may allow rainwater to seep in, leading to potential damage to the interior, including upholstery and electrical components. Long-term moisture intrusion can also create a favorable environment for mold growth and unpleasant odors.

The other outcomes associated with the other options are not relevant in the context of improperly secured windows. For example, increased fuel efficiency and reduced noise levels are not typically benefits associated with windows that are not properly closed. Instead, they may cause wind resistance and higher cabin noise. Additionally, enhanced visibility is not a likely result of windows that are not properly secured, as there may be obstructions or disturbances that could hinder clear sightlines. Thus, the most fitting outcome when windows are not secured is indeed moisture intrusion.