Can the grease be diluted with oil if it dries out?

Summary:

Q: The grease dries out and becomes hard. Can I add some oil to dilute it to keep the grease at the right consistency?

Answer: No. Grease is composed of base oil, thickener and additives. During use, the base oil is lost, causing the grease to dry out, but you cannot simply rely on adding oil to restore the oil content of the grease. If you find that the grease has dried out and become hard, you should add new grease instead of adding oil.

There are two reasons why you cannot add oil to grease: First, adding oil directly to dry and hard grease cannot effectively replenish the lost oil. Some people mistakenly believe that if the grease oil has drained out, just replenish it. In fact, the oil in the grease may not necessarily be added through this method. During the grease manufacturing process, the thickener and base oil must be effectively mixed under specific reaction conditions to produce grease. Therefore, the grease diluted by refueling by yourself cannot provide normal lubrication, which will cause poor lubrication and cause component wear.

Second, the machine has a requirement for the consistency of the grease. For example, the most commonly used one is 2# lithium-based grease. 2# refers to the consistency (softness and hardness) of the grease. If you add oil to the grease yourself, you will not be able to achieve the desired consistency. The required consistency, and the addition of diluting oil will also cause the loss of additives in the grease and the loss of the grease itself, especially the addition of certain light oils.

Sometimes the added oil and grease are indeed mixed evenly, but it does not mean that the performance of the grease is not affected. First of all, there are many categories of base oils and additives for grease. The oil we add is not necessarily the same as the base oil. Different oils and additives also have different effects. By adding oil, the performance of the grease will change, such as the base oil. If the viscosity is unqualified, the concentration of additives will be diluted, and the newly added oil may be incompatible with the components in the grease, causing the grease to denature and reduce its performance.

Correct approach:

If you find that the grease has become hard and dry, in addition to adding new grease, you should also consider further: Why does the grease become dry and hard? If the grease dries out and hardens repeatedly, it will directly cause poor lubrication and damage the components. First, check whether the current grease is selected correctly, whether the dosage is appropriate, and whether the grease is added at an appropriate time.

The selection of grease should be based on the equipment manufacturer's manual and the appropriate consistency (NLGI consistency grade) should be selected. In addition, attention should be paid to the appropriate base oil viscosity of the grease. Pay attention to the following reasons when the grease becomes hard:

1. The grease is contaminated: dust, mud, floating dust and similar impurities, which will cause the grease to dry out. When the grease is used, foreign impurities should be prevented from entering the lubrication system, which will not only affect the performance of the grease, but also cause wear and tear on the machine.

2. Incompatibility between greases: When changing the oil, have you ever paid attention to the type of grease you add each time? Are the grades the same? Are they the same product from the same brand? If you don't pay attention to these, then you are likely to get shot.

4. The base oil is oxidized: the selected grease has poor anti-oxidation ability.

5. High temperature of machine parts: If the bearings are filled with too much grease, overheating caused by mechanical conditions (improper installation, overload, etc.), insufficient lubrication may cause overheating problems during machine operation.

6. Vibration and centrifugal force: If the grease is subjected to long-term vibration or centrifugal force, oil separation will be aggravated. If the proper grease is not used, centrifugal force can dry out the base oil in the grease.

7. Exposure to special physical or chemical conditions: Grease is exposed to chemical substances, radiation, certain chemical salts, etc.