My local nissan service deptartment is very lacking in sevice. Do I have to use "nissan" service for my oiil changes inorder to keep my warranty? I would love to use someone who know what service really means. Last time I used nissan service they left mud in the drivers side carpet, didn't repair a lock even when asked, and failed to sign the service/warranty book. Please tell me I can use someone else and not jeopardize my warranty.