hey man how do u know its not kicking in? check ur vtec solenoid. its on the pass side on the side of ur cylinder head i believe if its engaging at 5800 rpms then it should be engaging at 4500 i believe it uses the same solenoid but i could be wrong.... excessive oil consumption does not sound vtec related issue. do u have a lot of some out of ur exhaust? or does oil drip on ground?