planet eclipse grease is not straight dow33... its based off of it as are most greases.
for warrenty purposes i would use the mac dev grease as recomended by mac dev. it works awsome im sure. if you really want to use something else, violent pb jelly would be your best shot, its some really good stuff.
Yeti PB Balls Out Photography Becker Industries
DPOT: Hotter than a 2 peckered billy goat