What maintenance task should be performed regularly to ensure a snowmobile runs well?

Checking fuel and oil levels is a crucial maintenance task for ensuring that a snowmobile runs efficiently. Fuel is necessary for the engine to operate, and maintaining the correct oil level is essential for lubrication, which helps to prevent engine wear and overheating. Insufficient fuel can lead to engine troubles, while inadequate oil can result in severe mechanical issues, potentially causing costly repairs or even engine failure.

Other options may have their merits, but they do not pertain directly to the routine operational readiness or immediate functionality of the snowmobile. Upgrading the skis, for instance, might improve performance or handling but is not necessary for regular operation. Painting the body serves a cosmetic purpose and does not influence the machine's performance. Replacing the battery is important, but it is typically not a regular maintenance task; it generally occurs when the battery fails or shows signs of deterioration. Regularly checking fuel and oil levels should be part of every snowmobile owner’s routine, ensuring reliability and longevity of the vehicle.