How much oil must be left before it needs to be changed?
2 Answers
Oil must be changed when less than 10% remains. The method for changing the oil is as follows: 1. Lift the car, remove the protective plate, and place a container under the oil drain screw; 2. Unscrew the oil drain screw, use an air gun to blow for two minutes at the oil filler port, then tighten the oil drain screw after draining and wipe it with a tissue to check for leaks; 3. Reinstall the protective plate and lower the car, then add oil through the filler port. The functions of oil are: 1. To reduce friction and high temperatures; 2. To minimize gas leakage and prevent external contaminants; 3. To prevent contact between water, air, acidic harmful gases, and parts; 4. To cushion the pressure rise in the engine cylinder port; 5. To clean dirt generated on the working surfaces of parts.
I've been driving for almost twenty years, and when it comes to changing engine oil, you can't just look at how much is left. Generally, you should change it when the maintenance cycle is due—for example, around 5,000 kilometers for conventional mineral oil and 8,000 to 10,000 kilometers for full synthetic oil. But if the oil level drops below the minimum mark on the dipstick, don't delay—top it up with the same type of oil immediately. Last time before a long trip, I checked and found the level had dropped below the 'L' line—I almost ended up with a seized engine, and the repair cost could've bought several cases of oil. Make it a habit to pull out the dipstick regularly. If the oil looks as black as soy sauce, has metal particles, or is unusually thin, change it early even if the quantity seems sufficient. Engine oil is like the lifeblood of your engine—don't skimp on it.
