I'm not sure the Niro has an idle speed similar to always on ICE engines. My BT OBD app doesn't seem to be working anymore otherwise I would check the engine rpm. But it certainly sounds like a very high idle when warming up, or a somewhat lower idle if I have left the heat on at a stop light. But never a low idle like you might expect with a DCT (which should be similar to a manual transmission car).I would not be surprised if you have greater than "normal" clearance in crank and/or rod bearings from that mileage and the oil pressure is actually low at idle speed for that reason