Well, I cannot speak to the theory of European vs American Lubricants. I can speak with some authority as to the exact reason for the failures, and then the remedy.
I had my LR3 serviced at the stealer from day one, exactly by the book to manufacturer specs. I had my Differential fluid changed at 75k, at that time, they advised me I needed a new differential rebuilt and quoted some price of 4-5k with labor.
I didn't have it replaced at that time, instead I started investigating if I could get the parts, etc. and what or who else might be able to do it. During this investigation I discovered that the parts were not available at the dealer, or anywhere else. I revisited the dealer on the subject, and discovered they were swapping the unit, not repairing it. No mention, just the usual dumb look, when I asked if there was a core swap, surcharge, etc. I then specifically asked if they could get the bearings and parts, and they claimed it couldn't be done. I asked them to give me the numbers on the bearings they claimed they had, and couldn't cross reference, no reply.
After lengthy investigation I found the bearings, and Ring & Pinion. After getting the parts in, and the additional bits needed, I located an Indy shop with good experience rebuilding differentials. So finally, I got it on the rack, and they pulled off the differential, and drained the fluid, etc. At 90k, just 15k after the fluid change, the fluid was milky and contaminated with water. Now, considering we live and a dry climate, and I have not forded any water (one time since I owned the vehicle) I don't understand how/why the diff oil is contaminated in such a short time. The conclusions that I can come to are that, either there is a design defect causing moisture to accumulate rapidly and not escape, or that the dealer did not actually change the fluids, as they claimed and charged me for. Now, you could argue that the damage was done from 0-75k miles, but that does not explain the water from 75-90k.
Now the lessons that can be taken from this based on talking with the Indy shop, is that water, and the resulting rust did the damage. So, I would have to say, it might be well advised to change your Differential Fluid every other oil change, or say every 14-20k miles. I don't currently have a warranty, but even if you do have a warranty, who wants to deal with getting repairs done, not having your vehicle, and all the other associated hassles. LR should change this fluid under warranty at least every other oil change, but if they will not, I would suggest you do it yourself, or pay the extra money to have it done.
Finally, the proof, I have several detailed photos, the only ones I know of, of the diff torn apart, and showing the rust and damage. The photo attached is the locking mechanism side of the assemble internals. The Indy shop, said in general it is a very slick designed differential, and well made, aside from the water. So, the only preventative before damage, is to change your Diff Oil's at least every other oil change in my opinion. After the damage, the only solution is to rebuild it, and then change every other oil change again. It could be said, that by doing every other, and monitoring the quality of fluids when drained, it might be possible to increase the frequency. And any time you operate in water, and extreme wet conditions, it might be well advised to drain and refill them.
If you want high quality images PM me with e-mail address and I will send them.
