Larry has some good points, but due to the long service intervals for transmissions & axles, I really like to use a good synthetic like Redline or Amsoil. I've seen Amsoil change an old BMW 635 CSi 5-speed manual transmission that was almost unshiftable in the Winter (until it warmed up), to a smooth shifter right out of the driveway. I will not be using Mobil 1 or Castrol Syntech any more due to information that I have been reading hear at the forum. Check out thread: http://www.peachparts.com/shopforum/showthread.php?threadid=31001
or
http://www.peachparts.com/shopforum/showthread.php?threadid=30429
for more info than you need on synthetic oils.

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Thanks,
Dave

1998 BMW 540i Sport
1995 E320
1992 400E
1989 BMW M3
1979 Triumph TR7 (1st car)
1986 BMW 735i (Sold)
1980 BMW 320i (Sold)