Just did a virgin oil analysis on a new bottle of BMW MTF LT-4 and got the results below: Also below is used oil analysis at 36,000 miles of what is supposed to be LT-4 also - this is in my 2009 JCW Clubmanwith 36K on the odometer: I was surprised by how thick the unused OEM fluid is (100C 14.8 cSt, 40C 70 cSt, with calculated VI of 223 ! ) Also surprised by how much it thinned out over 36K (100C 7.7, 40C 40.3) - still good numbers for a 6-speed Getrag. I was wondering if the previous owner added to or changed the gear oil from the factory fill, but he says no. Zeng on BITOG says (s)he's not surprised by the drop given the amount of viscosity index improver it must have to acheive 223 VI and that it just sheared down with use. Wondering if I should change it now with new LT-4 (have some), or use a more durable synthetic oil like Redline MT85 (75W85) (viscosities 12 and 62, VI 198) or Amsoil Manual Synchromesh Transmission Fluid MTF (5W30) (viscosities 10 and 50, VI 196), or something else entirely, or wait a year or so more to change it?