I've been using Mobil 1 Synthetic grease on my Astro van for several years. When I went to repack them at the 30K service interval it was like I had just repacked them. The grease was still bright red. I also use the Mobil 1 grease on the grease fittings with excellent results.

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Ray
1998 Mercedes E320, 200K Miles
2001 Acura 3.2TL, 178K Miles
1992 Chevy Astro, 205K Miles