a friend of mines truck he just bought oil pressure is fine when he starts it but he says as he keeps driving it slowly drops, and if he would be up to a red light it drops more, and when he takes it out of gear it goes all the way to the orange mark and the check engine light comes on, he says when he puts it back in gear or revs it up it will come back up, he took it to a shop today and they said the bearings were bad and were letting oil go by, i didn't know what the shop was talking about but i don't know much about these trucks either it is a 4 cylinder so any help would be appreciated