My Plymouth Laser O/M calls for ATF +3 or Dexron II or III, but I thought since it was made by Mitsubishi, that the Mitsubishi Eclipse version would call for Diamond ATF SP III instead. Have never seen a Mitsubishi Eclipse O/M to check if this a fact or not. Please advise.
It gets confusing these days with transmission fluid and power steering fluid both being sold separately. Then you have the many different alternatives listed in the owner's manual. Personally I would go with Dexron III.
I do know that from 2003 and up they use Mitsubishi spIII I am unsure of anything older.
I did a little goodle searching and older Mitsubishi made cars do use dexron in the ps system.
I would use whatever is in the owners manual. For my two mitsubishi made sebring coupes (03 and 04) the owners manual says diamnond star atf. Thus I have been using the chrysler atf+4 as the dealer would use.
To save money! Transmission requires the HFM'd ATF. The PSF doesn't and uses a cheaper fluid. Automakers don't make sense since many decisions are made by accountants.
I don't use SPIII in transmissions requiring it. I wouldn't bother using it as the PSF.
If your PS requires DexIII, then a good full synthetic DexIII equivalent ATF should be used.