Will 4S shops tamper with engine oil changes?

[Freya]

4S shops may tamper with engine oil changes without the car owner's knowledge. Here is a detailed introduction to engine oil changes at 4S shops: Recycling leftover engine oil: Be aware that sometimes 4S shops have leftover engine oil from servicing other vehicles, which they may use for the next customer. Therefore, the engine oil used for your car might actually be leftover from someone else's service. Occasionally, 4S shops may also mix unused engine oil with other brands, which can be harmful to the vehicle. Car owners should be cautious about this. Non-genuine engine oil: In principle, genuine engine oil should be used. However, when genuine oil is in short supply, 4S shops may use oil purchased from external sources. While these oils generally meet requirements, 4S shops often do not inform consumers about this practice.