Mobil One Synthetic ATF Multi-Vehicle lists as compatible with Mitsubishi Diamond SP-II Sp-lll. I'm using it now and no problems with trans.

Since this thread has been brought back I would like to add that the trans pan fluid pumps dry VERY quickly and so I would not recommend the turn on/turn off method. I have done this several times and prefer to use an assistant to turn the vehicle on and off while I add fluid non stop down the dip stick tube. If for some reason you need to stop adding then have the helper turn the truck off until ready to begin again. If the sump runs dry you foam the fluid which is also not good for the trans. I also buy one or two quarts over capacity of trans to make sure old fluid is flushed.