Replace the engine oil and oil filter (oil filter) The oil filter, fuel filter, air filter, and cabin air filter are commonly referred to as the "four filters" of a car. Although they may seem insignificant, they play a crucial role. The oil filter and fuel filter work to remove impurities from the oil and fuel, ensuring the engine runs smoothly. The air filter and cabin air filter also act as screens; without their filtration, even the best car won't go far, and the best air conditioning will emit unpleasant odors. When changing the oil, it's essential to replace the oil filter simultaneously to ensure the oil passages remain free of blockages. Of course, if upon inspection you find that these components were recently replaced, there's no need to change them again—save money where you can. Inspect and maintain the spark plugs Generally, spark plugs have a lifespan of 15,000 kilometers, while long-life spark plugs last no more than 50,000 kilometers. After a certain mileage, spark plugs can accumulate carbon deposits, and the electrode gap may widen. Carbon buildup increases engine fuel consumption, and a widened gap can make starting the engine difficult. When inspecting spark plugs, check the color of the burn and the electrode gap. Therefore, after purchasing a used car, it's important to inspect and maintain the spark plugs to ensure efficient ignition, prolong the engine's lifespan, and save fuel. Replace the timing belt and water pump If you've purchased a car that's over five years old or has exceeded 80,000 kilometers, the safest approach is to replace the engine timing belt, along with the water pump and auxiliary belts. Waiting until the water pump fails or the belt breaks can be dangerous. I once experienced this while driving a friend's car—the entire coolant leaked out, and I had to tow the car (costing me 2,000 yuan, which was heartbreaking). Note: Most used cars in the market are at least three years old, with many exceeding five years. Replace the transmission fluid Transmission fluid is essential for keeping the gear system clean but is often overlooked. After purchasing a used car, it's advisable to replace the transmission fluid with the manufacturer-specified type, especially for cars over five years old. Note: For cars older than five years or with over 80,000 kilometers, it's best to replace the transmission fluid. Clean the air conditioning system The car's air conditioning evaporator and blower are often enclosed in dark, damp conditions. Impurities, dust, bacteria, and viruses from the air can combine with condensation and clog components like the evaporator, accumulating dirt, nicotine, and mold. These contaminants breed quickly, producing foul odors that spread through the air conditioning, polluting the cabin and making passengers uncomfortable. Therefore, regardless of the car's age or mileage, cleaning the air conditioning system is a must after purchasing a used car—especially if the previous owner smoked inside the vehicle. Maintain the battery Check the battery's date or display status. If you notice the engine cranking weakly or the lights dimming, it's a sign the battery is nearing the end of its life and should be replaced as soon as possible. Car circuits are divided into low-voltage and high-voltage systems. When inspecting low-voltage components, check for burnt wires or poor connections, and also pay attention to the condition of the fuses. A battery typically lasts about two years, while spark plugs last up to 40,000 kilometers. Inspect the tires (traction) Some owners prioritize the car's appearance, so used cars may show little external wear. However, frequently used vehicles often have significant tire wear. When inspecting a used car, pay attention to the tread patterns and cleanliness of the tires, and ensure they have adequate traction. Some tires may look new or have deep treads, but the rubber may have hardened. Additionally, here's a tip: Most dealers replace severely worn tires on used cars they acquire, but the tires they use are usually the cheapest available!
