What is crucial for optimal mileage and handling of a vehicle?

Proper tire inflation is crucial for optimal mileage and handling of a vehicle because it directly affects how the tires make contact with the road surface. When tires are inflated to the recommended pressure, they provide the best possible grip on the road, which enhances handling, stability, and cornering performance. Correctly inflated tires also reduce rolling resistance, which can lead to improved fuel efficiency and mileage.

Under-inflated tires can lead to increased wear, reduced fuel economy, and poorer handling, while over-inflated tires can cause a harsher ride and decrease traction, especially in adverse weather conditions. Both conditions can adversely affect the overall driving experience and safety.

Tire tread depth is also important for traction and safety but does not directly impact fuel efficiency in the same immediate way that proper inflation does. Regular engine oil changes and transmission fluid type are essential for the engine's overall health and performance but are more focused on the internal workings of the vehicle rather than its handling and mileage directly linked to tire performance.