Mixing lubricating greases can lead to several complications.

Mixing lubricating greases can lead to several complications. Here's why it's usually recommended against:

1.     Incompatibility Between Thickening Agents: Greases are typically made up of base oil and a thickening agent. Common thickeners include lithium, calcium, aluminum, and polyurea. If greases with different thickeners are mixed, they can react with each other and cause the mixture to soften or harden. This can result in the grease no longer providing the necessary lubrication for the application.

2.     Oil Separation: Mixing greases can cause oil separation, where the base oil separates from the thickener. This can reduce the lubrication properties of the grease and increase wear on machinery.

3.     Change in Performance Characteristics: Different greases have different additives that provide specific performance benefits, such as anti-wear, anti-corrosion, or extreme pressure resistance. Mixing greases can dilute or negate these additives, potentially reducing the grease's performance.

4.     Alteration of Dropping Point: The dropping point of a grease is the temperature at which it becomes fluid enough to drip. Mixing greases can change this point, potentially making it unsuitable for high-temperature applications.

5.     Variation in Viscosity: Greases have varying viscosities based on their intended application. Mixing them can result in a product with unpredictable and undesired viscosity, which can affect the lubricating performance.

6.     Increased Risk of Contamination: Each time a grease is handled or transferred, there's a risk of contamination. Introducing a different grease can bring in contaminants that can cause wear or damage.

7.     Cost Implications: If mixed grease causes machinery to fail or reduces its efficiency, this can result in downtime and increased maintenance costs. It's often cheaper in the long run to ensure that the correct grease is used consistently.

8.     Warranty and Specification Issues: Using the wrong grease or mixing greases might void the warranty on a machine or component. Many manufacturers specify a particular type of grease for their equipment, and deviating from that specification can lead to complications.

9.     Difficulty in Predicting Behavior: The resultant mixture of two or more greases can behave unpredictably. This can make it hard for maintenance personnel to predict how often re-lubrication is required or when the grease might fail.

For these reasons, it's essential to carefully select the correct grease for each application and avoid mixing different types. If there's a need to change the type of grease being used, it's important to clean out the old grease thoroughly before applying the new one.