Using inspection of lubricating grease correctly and at the right time is essential for operating performance and equipment life. However; technicians do not always have specialized testing equipment. Therefore; assessing grease condition by sight and touch is an important practical skill for field maintenance.
This article explains how to identify whether grease is still serviceable or has degraded using the basic senses of sight and touch so technicians can make fast; accurate decisions.
1. Why inspect lubricating grease?
Lubricating grease is a mixture of:
- Base oil (typically mineral or synthetic oil),
- Thickener (metal soaps such as lithium and calcium; or non-soap thickeners),
- And additives (anti-oxidation; anti-wear; anti-rust; etc.).
After service; grease can become contaminated; lose its lubricating properties; or degrade due to temperature; moisture; load and operating time.
2. When should grease be checked by sight and touch?
- During routine maintenance; inspect the equipment.
- When you observe abnormal conditions: heat; noise; vibration or grease leakage.
- When disassembling equipment for cleaning or bearing replacement.
When no specialized grease-analysis equipment (such as a viscometer; FTIR or ferrography).
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Guide to visual grease inspection
3.1. Check the color
| Condition | Typical appearance |
| New; good grease | Uniform and glossy; with its original color (off-white; light brown; green or red depending on the type) |
| Oxidized grease | Dark or cloudy; losing gloss and possibly turning brown or black |
| Water-contaminated grease | Milky and emulsified |
| Grease contaminated with dirt or metal | Gray or black; or containing tiny bright particles (metal debris) |
👉 Note: An abnormal color change is the first sign that grease has degraded or become contaminated.
3.2. Check consistency
- Good grease: uniform consistency with no oil/thickener separation.
- Failed grease: separated (oil bleed); lumpy; dry and tacky; or excessively soft.
👉 Observe the grease surface on the bearing or in the gearbox. Separate oil indicates loss of mechanical stability.
4. Check grease by touch
⚠️ Safety note: Wear nitrile gloves if hazardous additives may be present. Do not touch grease with open wounds.
4.1. Assess consistency and tackiness
- Take a small amount of grease and rub it between your thumb and index finger.
| Feel | Meaning |
| Smooth and even; with no foreign particles | Good grease |
| Soft; with oil bleeding when rubbed | Oil-separated grease; replace it |
| Tacky; dry and difficult to spread | Grease has lost base oil or dried due to high heat |
| Small gritty particles | Metal debris or dirt contamination – wear risk |
4.2. Check recovery
- Rub and stretch the grease between two fingers; then release it.
- Good grease will have slight elasticity and return to its original shape.
- Failed grease will string-break; become uneven or visibly separate
5. Signs that grease must be replaced immediately
- Severe discoloration (black; cloudy white or mottled).
- Burnt odor or signs of thermal damage.
- Clear oil separation or lumping.
- Foreign matter (dust; water or metal debris).
- Dry; tacky feel rather than smoothness.
6. Practical notes
- Do not mix greases with different base types (for example; lithium and calcium greases may react).
- Store grease in a dry; cool; closed place; away from direct sunlight and moisture.
- Always use grease with a clearly defined shelf life and follow the manufacturer’s recommendations.
- inspection of periodically inspect slow-speed; heavily loaded bearings – these locations can degrade grease quickly.
Conclusion
Although visual and tactile grease inspection is simple; it is critical in field conditions where specialized equipment is not always available. Technicians skilled in this method help reduce failure risk; maintain stable machine performance and lower maintenance costs.
Where to buy genuine SKF lubricating grease?
If you are looking for a reliable source of genuine SKF lubricating grease; LDT Company is a leading supplier of high-quality lubricating oils and greases. We provide genuine products that deliver optimum lubrication performance for industrial machinery and equipment.
Benefits of buying from LDT:
- Genuine SKF products with complete certification
- Expert guidance to help customers choose the right grease
- Competitive pricing and fast delivery support
- Professional after-sales and warranty service
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Address: 121-123 To Hieu Street; Nguyen Trai Ward; Ha Dong District; Hanoi; Vietnam
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