Originally Posted by Quicksilvers

If your Z is in N/A form I would recommend installing the Denso replacement spark plugs in your VQ37HR engine because I have seen them last the longest. Your best bet would be to purchase the replacement spark plugs of your choose online or at your favorite auto parts store and install them yourself if you can or have a reputable shop you trust install them for you. To bring your Z to the Nissan dealership service department should be your last resort. If you bring your Z to a shop to have your replacement spark plugs installed always ask for your old spark plugs back so you can check the condition of them and so you know they actually changed them. I dread ever bringing my Z to the Nissan dealership service department.