I have a 2002 X5 3.0 with auto trans. I use the Pentosin ATF Synthetic Trans fluid only. I have had no problems with my transmission. I did the first service at 100K miles. I should have done it sooner. The fluid was black. I did another service about 20K miles later and the fluid looked a lot cleaner. I did change the filter both times. As for the front and rear diffs, I use a full synthetic gear oil. I did not add any additive to fluid.