Check and change the oil. No single step will help an engine last more than regular oil and filter changes will.
Conversely, nothing will destroy an engine faster than neglecting oil-level checks or fresh-oil changes
Flush the cooling system and change coolant once a year. A 50/50 mix of coolant and distilled water will keep the cooling system in good shape and prevent corrosion and deposits from building up inside the cooling system.
Protect the interior plastic by parking the vehicle in the shade, using a window deflector screen, and applying a UV protectant to prevent the plastic and vinyl from drying out.
Brake fluid is hygroscopic. This means it is adept at attracting moisture. Moisture causes components to corrode and fail. Replace fluid and bleed system once a year. Brake fluid is cheap. Calipers, hoses, and sensors are expensive.
Frozen Wiper blades
Hate frozen wiper blades? Soak a cloth in pure rubbing alcohol and wipe each blade. This will keep them from freezing to your windshield.
Old or low power steering fluid makes it difficult for a driver to steer his vehicle. Flushing this fluid every 30,000 miles improves handling and performance!