Here are a couple of 'used' posts that I wrote in days gone past.
Greases have a number of characteristics, one biggie is the Drop Point. When soap-based grease is heated until a critical temperature is reached the gel structure breaks down, and the grease becomes liquid. When grease is heated above the Drop point and then allowed to cool it usually does not fully regain its grease consistency therefore it will not lubricate.
Lithium-soap greases have very good stability and good water resistance. They have a buttery texture and are a brownish-red color. The 'soap' is actually a metallic salt resulting from the interaction of fatty acids or esters typically with an alkali. Lithium soap greases have a Drop point of ~350ºF. LiSoap grease is a good general purpose lubricant/protectant for low temperature and wet environments.
Moly Paste has a non melting, lubricating base containing a high percentage of low-friction molybdenum disulfide. It is a thick paste type grease that has a temperature range up to 750°F when in contact with air. Moly paste 'plates' the work surfaces with moly disulfide which remains and protects working surfaces even if the grease gets squeezed out. Moly also fills microscopic voids in surfaces. Moly has a film strength of 300,000 psi and adheres tenaciously to metal surfaces. Moly paste is almost always blue to black in color. One last trait is that moly does not fling off at high speeds.
Wheel Bearing Grease is also a lithium complex grease which contains petroleum base oils. The primary application for it is in high temperature operations such as wheel bearings. It may be used at continuous operating temperatures up to 325°F. It prevents rust and corrosion, reduces wear, and provides extreme pressure protection. Dropping point is ~500° F. Color typically white.
T120TT then asked:
Can wheel bearing grease be safely substituted for lithium soap based grease of a lower Drop point? I assume the reverse wouldn't be true. Correct?
Down the slippery slope.....
Generally you can substitute white for red-brown grease in non critical applications when the temperatures will be well below the drop point, thickness (viscosity) isn't critical and water exposure will be minimal. When da BIG BOOK says Moly, use it.
Soap based greases are generally in a family of 'short fiber greases'. Most soap-thickener fibers are microscopic and the grease appears smooth; if the fiber bundles are large enough to be seen, the grease appears fibrous. The texture of a grease is observed when a small portion of it is pressed together and then slowly drawn apart. Texture can be described as:
- Brittle — ruptures or crumbles when compressed
- Buttery — separates in short peaks with no visible fibers
- Long Fibers — stretches or strings out into a single bundle of fibers
- Resilient — withstands a moderate compression without permanent deformation or rupture
- Short Fibers — short break-off with evidence of fibers
- Stringy — stretches or strings out into long fine threads, but with no evidence of fiber structure
Other significant differences between similar appearing grease can be
Penetration (mechanical, not www.xxx)
Oil separation
Viscosity @ 40°C & 100°C
Oxidation resistance
Resistance to water
3 & 4 ball wear ratings
[common sense] Substituting grease for side stands, pivot points and perhaps lightly loaded bearings should be fine. It gets a bit more adventurous at the higher loaded steering head
ball bearings as opposed to roller bearings. [/common sense]
