Three numbers and one chemistry decide whether a grease belongs in a joint: the NLGI consistency grade, the base oil viscosity, and the thickener type. For most excavator pins, an NLGI 2 lithium complex grease with a base oil near ISO 220 and EP additives is the working default, and swing circles and heavily loaded bushings often call for molybdenum. The thickener matters because greases are not interchangeable: lithium and polyurea thickeners are incompatible, and mixing them can soften a grease until it runs out of the joint or harden it until it blocks a line. Color is not an identifier of anything.
Mixing greases of different thickeners
| Combination | What usually happens |
|---|---|
| Lithium complex plus polyurea | Incompatible. Commonly softens sharply, and the joint throws the grease out instead of holding it. |
| Lithium complex plus calcium sulfonate | Incompatible in general service. Can harden and plug a grease line or a distributor port. |
| Two lithium complex greases, similar base oil | Usually compatible. Confirm base oil viscosity and EP additive before the first full purge. |
| Polyurea plus polyurea, different base oils | Thickener compatible; the base oils may not be. Viscosity mismatch changes film strength at temperature. |
| Clay thickened plus most thickeners | Clay is broadly compatible. The risk moves to base oil viscosity and additive clash rather than the thickener. |
How to confirm it
- Read the specification before the shelf
Find the grease specification in the operator manual or on the decal at the grease point. It will state a grade and often a base oil viscosity and an additive requirement. Matching a specification is a decision; matching a color is a guess.
- Establish what is already in the joint
Use service records, drum labels and supplier data rather than appearance. If the history is genuinely unknown, assume incompatibility and plan a full purge rather than topping up and hoping.
- Decide between staying and switching
Staying on a grease that meets the specification is almost always right. Switching is justified by a real problem: water washout, high temperature, excessive pin wear, or a supply that no longer exists.
- Purge fully when switching thickener
Pump new grease until it appears clean and consistent at every point served by that line, not for one stroke. A line holds enough old grease to contaminate the joint for days, and a distributor holds more.
- Match the grease to the duty, not the machine
Pins and bushings want EP and often molybdenum; high-speed bearings want a lower NLGI grade and a lighter base oil; wet or washed areas want calcium sulfonate. One grease for the whole machine is a compromise, and it is often an acceptable one if it is the right compromise.
- Control storage and transfer
Keep drums closed, wipe fittings before coupling, and never pump from an open bucket. Most grease contamination arrives with the grease, and a dirty coupler injects grit straight into a bushing.
What to do about it
If a joint is already packed with an incompatible grease, purge it completely and re-grease on a short interval for the first few cycles so any residual mix works its way out. Watch for softening and leakage during that period, because that is when the incompatibility shows.
If grease is running out of a joint after a change, suspect incompatibility or an over-filled bearing rather than a failed seal. Softened grease escapes; a failed seal usually shows as a track of oil rather than a clean grease loss.
If a joint is dry and squealing while the grease gun works, the passage is blocked, not empty. Clear the fitting and the line before adding more pressure, or the grease will find the path of least resistance around the bushing instead of into it.
For high-load pins showing rapid wear, a molybdenum-fortified NLGI 2 grease is the usual step, and shortening the interval does more for life than changing brand.
Grease, filters and the fittings that carry them are supplied by Guangzhou Shenyue Machinery Technology Co., Ltd., with 3,000+ part types on the shelf and 100,000+ part numbers available to order, including the five lines the company is an authorized dealer for: Garrett, Mitsubishi Heavy Industries (MHI engine parts only, covering 6D34, 6D31 and 6D24), TONGMYUNG, NIKURA and Marusan.
Parts you may need, by grade
| Part | Grades commonly quoted |
|---|---|
| NLGI 2 lithium complex EP grease | Genuine; OEM-quality; aftermarket. The general-purpose default for pins and bushings. |
| Molybdenum-fortified NLGI 2 | Genuine; OEM-quality; aftermarket. For high-load pins and worn bushings. |
| Calcium sulfonate grease | OEM-quality. Preferred where water washout is the dominant problem. |
| Polyurea grease | Genuine; OEM-quality. Specified for some sealed bearings; never mix with lithium. |
| Grease fittings, couplers and lines | Genuine; OEM-quality. A worn coupler pumps grit as efficiently as grease. |
Need the parts this covers?
Send the machine model, serial number and the part numbers you need. We confirm fitment before payment and state the grade of every line — genuine, OEM-quality or aftermarket.
Request a quoteFrequently asked
Can I mix two greases if both say NLGI 2?
Only if the thickener chemistry matches. The NLGI grade describes stiffness, not chemistry, and two NLGI 2 greases can be completely incompatible. Lithium complex and polyurea are the classic example: both are common, both are NLGI 2, and mixing them can soften a joint until it throws grease.
Is molybdenum grease better everywhere?
No. Molybdenum disulfide helps in slow, heavily loaded sliding contacts such as pins and bushings. In high-speed bearings it can be unnecessary and in some sealed applications it is not what the specification calls for. Fit the grease to the duty, and when one grease must serve the whole machine, pick the one that meets the most critical point.
Why did a joint start leaking grease after a change?
Softening from thickener incompatibility is the usual reason, and it looks like leakage because the grease has lost its structure. The other possibility is simple over-filling of a sealed cavity. Purge, refill with a known product, and watch the next few cycles before replacing anything.