Short answer
A breaker bushing works under a load found nowhere else on an excavator: dozens of blows a second, high temperature and constant dust. General purpose excavator grease cannot hold its film under that, thins as it heats and is pumped out of the bushing. Breaker grease is made to stay in place under impact and to survive heat; the solid lubricants in it leave a buffer against metal-to-metal contact even if the film breaks. The right grease type is described in your breaker manual.
Why conditions in a breaker bushing are different
Excavator pins and bushings move slowly and carry steady loads. There, the job of grease is simple: keep two surfaces apart.
In a breaker bushing the movement is sudden and repetitive. The tool makes a small movement inside the bushing with every blow, and that repeats dozens of times a second. The tempo acts like a pump constantly trying to push the grease film out.
Heat sits on top of that. Part of the impact energy turns into heat and the bushing area reaches temperatures found nowhere else on the machine. A grease that thins with temperature cannot stay where it is needed at exactly the moment it is needed.
What to look for in a breaker grease
- Staying put at high temperature: it must not run out of the bushing as it heats.
- Film strength under pressure: it must survive between two surfaces at the moment of impact.
- Solid lubricant content: this leaves a buffer against metal-to-metal contact even if the film breaks for an instant.
- Tackiness: as it is pushed out through the bushing clearance it should carry dust with it.
- Resistance to water and dust: it must not wash away, nor turn into an abrasive paste when it picks up dust.
Why we do not print the figures
Grease grade, drop point and additive content depend on breaker size, working temperature and how it is lubricated. A grease that is right for one breaker can be too stiff for another and block the line of an automatic system. The right specification is in your manual; if you do not have it, send us your model code and we will tell you which properties to look for.
What the wrong grease looks like in practice
The first sign is where the grease goes. The right grease seeps slowly out of the bushing mouth, mixed with dust. The wrong grease either never appears, because it thinned and ran inside, or is completely expelled within one shift.
The second sign is the bushing itself. An under-lubricated bushing comes out with a scored, polished inner surface rather than an even one. That look means the film was breaking.
The third is the tool shank: a tool running dry shows discolouration and stiffness, and in advanced cases binds inside the bushing.
The mixing problem
Greases with different thickener systems can lose their consistency when mixed: the mixture either stiffens and blocks the line, or softens and runs out. If excavator grease and breaker grease go through the same nipple, that risk is real.
The practical rule when changing grease is to purge the old one as far as possible: keep pumping the new grease until it comes out of the bushing mouth clean.
On an automatic system, do not change grease type when replacing a cartridge; the system is set up around one grease.
Same grease in summer and winter?
Sometimes, but not always. A grease that stiffens in the cold struggles to flow in the line of an automatic system, and feeding effectively stops. One that stays thin in the heat cannot hold in the bushing.
If you change grease by season, purge the line and bushing of the old one during the change, and review the system setting against the consistency of the new grease.
If you work in a very cold or very hot climate, choose the grease together with your supplier; no single product suits every condition.