i'd say take it to the dealer, my car had high idle for a while, then for a while normal, then all of a sudden could not go past 40 one morning. Trust me from my experience GO TO THE DEALER, its the engine/cat/pcm/power valve-reflashing take care of that beside the consumtion. Again take it to the dealer first, get documentation. All my problems went away with a reflash(and a $3000 rebuild nissan didn't want to pay for, i still dont have a cat-source of oil problem that ecm started!)