I have only heard of using lithium grease for trailer bearings because it is water resistant. I do know that you absolutely canNOT mix petroleum grease and lithium grease...you need to completely clean off the bearings 100% before you pack with the other, but it is a good idea to do that anyways. Personally I would stick to petroleum since it is more widely used for autos IIRC.

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TC
Current stable:
- 2004 Mazda RALLYWANKEL
- 2007 Saturn sky redline
- 2004 Explorer...under surgery.

Past: 135i, GTI, 300E, 300SD, 300SD, Stealth