I do not believe that Idemitsu makes an oil that is not synthetic for the U.S. Same goes for a Subaru labeled version.So would the conventional oil that they are recommending for my Legacy be the Subaru brand (Idemitsu)? Or more likely something like Pennzoil or Quaker State etc?
https://www.idemitsulubricants.com/idemitsu/engine-oil