What task is necessary to prepare for the drive to New Mexico?

Filling up the gas tank is a critical task for preparing for a drive, especially over long distances such as from one state to another. Ensuring the vehicle has enough fuel before starting the journey helps to avoid any unexpected stops and delays. It is a practical step that directly impacts the ability to complete the trip successfully.

While checking the oil, washing the car, and packing luggage are also important preparatory tasks, they do not directly relate to the immediate requirement of having enough fuel to begin and sustain the drive. Thus, in the context of preparing specifically for a drive, ensuring the gas tank is full is the most necessary step to take.