How to Determine if Car Engine Oil Needs to be Changed?

[ColtonLee]

Methods to determine if car engine oil needs to be changed are: 1. Check the oil quality - if the color turns black and smells acidic; 2. Use your fingers to check if the oil still has viscosity; 3. Difficulty in shifting gears when starting a cold engine. The steps to change engine oil are: 1. Remove the air filter, clean it with an air pump, and reinstall it; 2. Lift the car, unscrew the drain plug to release the old oil, and remove the oil filter; 3. Add approximately 3.5 liters of new engine oil. The functions of engine oil are: 1. Reduce friction and high temperatures; 2. Cool down the engine; 3. Clean and remove impurities; 4. Absorb shocks; 5. Prevent rust and corrosion.