Which of the following is NOT an item to check during a trip?

Checking gas mileage is typically not considered a critical safety or operational check to perform before or during a trip. While monitoring fuel efficiency can be beneficial for overall driving performance and budgeting for fuel expenses, it does not directly affect the safety or functionality of the vehicle.

On the other hand, checking the windscreen washer fluid is essential for visibility, as dirty or obstructed windshields can lead to accidents. Temperature gauges are crucial for monitoring engine health and preventing overheating, which can result in severe mechanical failure on the road. Likewise, mirrors are vital for ensuring proper visibility of the surroundings, including blind spots, which is key for safe maneuvering and following traffic regulations.