THIS IS FOR N. AMERICAN AUTOMATIC TRANSMISSION X3s ONLY. This does not necessarily apply to X3s sold elsewhere in the world.
Basic E83 Transmission Facts
The 2003-2006 US E83 (X3) models came with a GM 5L40-E MX5
automatic transmission. The BMW name for this transmission is the A5S 390R. This transmission was made in Strasbourg, France. It is a 5 speed steptronic transmission. No US model used the ZF transmissions. (If you have a US X3 without a GM tag on the driver's side of the transmission, please post so I can correct this.)
The 2007-2010 US E83 (X3) models came with a GM GA6L45R
automatic transmission. The BMW part number for this is simply GA6L45R. This transmission was also made in Strasbourg, France. It is a six speed steptronic transmission. No US model used the ZF transmission. (Again, if your X3 is from the US and it does not have a GM transmission, please post.)
For 2003-2006 X3 models
, BMW specified an ever changing list of automatic transmission fluids (ATF) as these fluids became obsolete over time. The current recommendation from BMW is DEXRON-VI ATF, which means the fluid conforms to the GM DEXRON-VI specification. (AKA DEX-VI, Dexron VI, Dexron 6, Dex 6, DEX 6, etc).
For 2007-2010 X3 models
, the recommended fluid has always been DEXRON-VI.
DEXRON is a GM trademark. GM alone determines whether an ATF may use the DEXRON mark on the product label. GM suggests that ALL of their automatic transmissions (from 1968 on) should now use a DEX-VI ATF, and BMW now recommends DEX-VI for all 2003-2010 US BMW X3s. Here are the facts about DEXRON: Wikipedia DEXRON
Tips on Fluid / Filter Change
BMW claims the Automatic Transmission Fluid (ATF) is lifetime, and should never be replaced. There is a sticker on the bottom of the transmission pan that says to never change the fluid. Some BMW dealers now refuse to change transmission fluid. In engineering school I learned that no oil lubricates forever. I have a friend who was an engineer that tested transmissions at Allison Transmission for 20 years, and he agrees.
So here is my advice, which you can follow at your own risk, or ignore completely.
1) Somewhere between 50K and 100K miles, change the filter, and drain and fill the fluid. I suggest the MEISTERSATZ filter. Here is a tutorial on this process for the same transmission in a BMW E46: ATF Filter Tutroial
. Here's my handy PDF summary of this tutorial, with full size pics ready for printing: PDF of Tutorial with Pics
2a) For a 2007-2010 X3, use a trustworthy brand of DEX-VI. Any brand that is actually licensed by GM should work, even Wal*Mart brand. I wouldn't use that, but I'm paranoid.
2b) For a 2003-2006 X3, use a trustworthy brand of DEX-VI, or a fully synthetic ATF. I say this because Mobil 1 Synthetic ATF is NOT
DEX-VI certified (I wrote to Mobil and asked), but it seems to have better viscosity ratings across the board than Mobil Dexron-VI. Also, Mobil Dexron-VI ATF is a blend and not purely synthetic, and I like synthetic.
Here are the specs for Mobil 1 Synthetic ATF and Mobil Dexron-VI ATF: Mobil Dexron-VI ATF
vs Mobil 1 Synthetic ATF
3) Finally, "Power Flushing" is safe AFTER THE FILTER HAS BEEN CHANGED AND THE FLUID HAS BEEN REFILLED. I spoke with the owner of Pat's Automatic Transmission Service in Broomall, Pennsylvania last week. He said that while I could do a drain, fill, and then have him flush it, that this would cost a fortune. The problem is that the transmission and torque converter combined hold about 10 quarts of fluid. The transmission specialist told me that as soon as the clean fluid is pulled into the transmission, it mixes with the old fluid that is already in there. So for the flush, they just keep pumping in new fluid until the out-flowing fluid is clear. For a 10 quart transmission, he estimated it would take 20 quarts of new fluid to do the flush, and that's after you've used 6 or 7 quarts on the drain and fill. His recommendation was to change the filter, refill the transmission, drive 50 miles, and then drain from the drain plug and refill again. Otherwise, you're going to spend big bucks on fluid.
If you are an engineer at a transmission company, a chemist with a lubricant company,or an ASE Certified Master mechanic, I would love to hear your thoughts. If anything that I've stated as a fact above is false, and you have evidence, please post so that I can make corrections. At some point GM will supersede DEX-VI with a new specification, so if you're reading this years from my original posting date, please keep that in mind.
Originally misstated 5L40-E as 4L40-E, which does not exist
Added links to the Wikipedia site for both transmissions
Edit paragraph about power flushing to include expert advice