Originally posted by mikel
Depends on who you ask. Dodge puts their opinion right on the side of the transmission. There is a sticker there that threatens voided warranties and possible global warming if their specified lube isn't used.
People here have used everything from Amsoil engine oil to a Redline gear lube to Royal Purple Synchromax.
You'll most likely get a bunch of opinions, so I might as well get mine in at the start. Keep in mind that my transmission is out of warranty so your situation may be different, but I'm running the Royal Purple Synchromax. I started using it in hopes of better shift quality and it does *seem* to shift better, but it is also entirely possible that it is just me wanting to validate the $$ for the RP to myself (not that the factory fill would be any cheaper).
Good Luck,
Mike