Jun 12, 2018
After talking with lubricant engineers, I've learned:
-the only difference between blue, red or green grease is the type of dye used to give it color. The normal color of "raw" grease is yellowish-gold. One exception is molybdenum grease, which is blackish.
-molybdenum grease handles high pressure well, and is recommended in situations like suspension pivots or steering components where there could be a lot of pressure pressing components together, but no full "rotation" of those components to routinely work fresh grease between the components.
-if you're having trouble with grease guns "air-locking" after you install a fresh tube of grease, try storing the tubes of grease vertically. Storing tubes vertically reduces the chance of the grease flowing sideways in the tube and creating an air bubble the full length of the tube. (I won't guarantee that to solve the problem, but it could help.)
-thicker grease is not necessarily better grease. Super-thick grease may actually not flow between tight-fitting parts as well as thinner grease, starving those parts for lubrication. On the other hand, very thin grease may flow too easily, drain away from components and, again, starve them for lubrication. Use the grease recommended in the owner's manual for a particular machine to ensure proper lubrication.
-there is no "universal" grease that can be used in every situation, but...polyurea grease is a good all-purpose grease for everything from u-joints to wheel bearings to roller bearings.