Why do 4S shops add engine oil to the highest point?

[JasmineLynn]

4S shops add engine oil to the highest point because the car is in a hot state when owners go to 4S shops for maintenance. There are two points to note when adding engine oil: 1. When selecting engine oil: it is necessary to strictly follow the engine oil grade specified in the car manual. If there is no engine oil of the same grade, you can use a higher grade, but you cannot use a lower grade instead; 2. When adding engine oil: the amount of engine oil added should be slightly lower than the standard scale. Too much engine oil will increase the rotation resistance of the crankshaft, reduce the output power of the engine, and excessive engine oil will enter the combustion chamber to participate in combustion, causing the vehicle to burn engine oil, emit blue smoke, and even increase fuel consumption.

[MiaRose]

The dipstick has minimum and maximum level markings, with filling to the maximum primarily serving as a safety buffer design. Engine oil naturally depletes during operation due to factors like minor burning or evaporation from piston movement. If filled only to the minimum, oil levels could drop to critical thresholds after a few hundred kilometers, risking insufficient lubrication that may cause overheating, severe component wear, or even engine seizure. 4S dealerships typically follow industry standards and manufacturer guidelines by adding slightly extra to ensure worry-free driving until the next service. An added benefit is that maintaining higher oil levels ensures all moving engine parts remain lubricated while reducing the risk of oil pump air ingestion, preventing performance issues from low oil pressure. Although overfilling may potentially cause leaks or foaming, the maximum line represents a tested safe limit—staying below it poses no issues. Regularly checking oil levels yourself and cultivating this habit can significantly extend your vehicle's lifespan.

[StevenMarie]

We always fill the engine oil to the maximum level for customer peace of mind. After driving, the oil level gradually decreases; if we only fill to the minimum mark, customers might notice low oil levels within days and return complaining about poor service, which harms our reputation. Adding extra oil provides a buffer, reducing the chance of mid-journey issues and avoiding costly engine overheating or major repairs. Most car owners rarely check their oil levels, so this step helps maintain stable vehicle conditions. This isn't about selling more oil products—it's a core part of professional service to ensure smooth and worry-free driving after every maintenance. Cost-wise, while slightly more oil is used, the reduced failure rate saves everyone trouble overall. Remember to check your oil every few thousand kilometers—a small habit that protects your big machine.

[VanMaximus]

Some people think filling up the oil is just to make extra money, but in reality, it's to prevent potential risks. The area between the min and max marks on the dipstick is the safe range; oil is consumed while the engine is running, especially in city traffic with frequent stops and starts, causing the oil level to drop quickly. Filling to the top ensures a buffer—even if it drops to the min zone, there's still a long way to go before lubrication becomes insufficient, preventing damage to bearings or cylinders. Dealerships know low oil levels can cause major failures, leading to costly repairs and potential liability. From a safety perspective, this practice is reasonable; while overfilling is harmful, the max mark is the designed upper limit as a warning. Developing a habit of regularly checking oil levels helps detect abnormalities and address them promptly.