What lubricant to use for a stiff car door?

[StWyatt]

For a stiff car door, you can use either grease or engine oil for lubrication. 4S shops typically use liquid grease, but be careful not to apply too much as it can accumulate excessive dirt. Relevant information about grease: 1. Concept: Grease is the common name for calcium-based lubricant, formally known as industrial lubricating grease. It is made by thickening medium-viscosity mineral lubricating oil with natural fatty acid calcium soap. 2. Characteristics: Calcium-based lubricant has excellent water resistance, is not easily emulsified or deteriorated when exposed to water, and can be used for lubricating mechanical components in humid environments or those in contact with water. It also has good shear stability and thixotropic stability, meaning it remains on the working surface after agitation and maintains a sealing effect without being thrown off.