So here's an interesting one, that I really didn't expect from Toyota:
It's time (well, probably a few 1000 miles late on the rear) for me to do the first diff and transfer case oil changes on my 4Runner. I was going to go buy the OEM recommendation and use the called for oils: Toyota 75wt-85 for the diffs, and 75wt for the transfer case. The 75wt doesn't seem to exist, even at the dealership. The 75wt-85 is not available at the dealership. It's available from Amazon for $32/liter. Yes, $32/liter (and it is sold by the liter).
After much researching on the Toyota forums, it appears these "use them or void your warranty!!!" oils are just used at the factory for eeking out a tiny little bit more MPG for CAFE standards. Even the dealers don't use the Toyota oils. The oil they use is apparently some bulk labeled Toyota oil, but made by Mobil, and likely 75wt-90. It looks like most people just end up using Mobil 1 Delvac 75wt-90 for everything and call it good. And the Mobil 1, considered a premium grade, is $40/gal vs the $32/liter for the Toyota oil. If the Toyota 75wt could be purchased, and I bought it and the Toyota diff oil, it would run me something like $250 just for the oil to do it myself. That might be more than the dealer charges for the work.
While I could see the marketing aspect of not selling the "warranty oil" to do-it-yourselfers so that dealerships can charge for the service, the fact that they also don't use it at the dealership is pretty ridiculous from the warranty side. A guy on one of the Toyota forums even called Toyota and went through like a half dozen people who couldn't provide him an answer on the oil. He posted some of their responses which would do a B movie scheister lawyer credit.
Anyway, I kinda thought it was funny, other than the couple of hours I wasted on research and rabbit holes to make sure I was using the right stuff.