What is the most important car maintenance?

The most critical item in car maintenance is the regular replacement of engine oil and oil filter, which directly affects the lubrication efficiency and lifespan of the engine. Mineral oil should be replaced every 5,000 kilometres or 6 months, while fully synthetic oil can extend the interval to 10,000-15,000 kilometres. Next is brake system maintenance, including inspecting brake pad thickness every 40,000 kilometres (replace if below 3mm) and changing brake fluid every 2 years or 40,000 kilometres (immediate replacement required if water content exceeds 3%). These measures are vital for driving safety. Tyre maintenance should also be prioritized: monthly pressure checks (refer to door frame specifications), rotation every 10,000-20,000 kilometres, and regular inspections of tread depth (replace if below 1.6mm) and sidewall damage like bulges or cracks. Additionally, replace the air filter every 10,000-20,000 kilometres to maintain clean engine airflow; change the cabin air filter annually or every 10,000 kilometres for interior air quality; and replace spark plugs according to material type (conventional: 20,000-30,000 km; iridium/platinum: 60,000-100,000 km) to ensure proper ignition. Core procedures also include periodic replacement of transmission fluid (manual: 60,000 km; automatic: 80,000-100,000 km) and coolant (every 2-3 years or 40,000-60,000 km). Proper maintenance not only prolongs vehicle longevity but also ensures optimal performance and safety across powertrain, braking, and electrical systems.