I have a V6 (older style, 2002) 2.6 SRI Vectra. It's due a service soon, but I was wondering if anyone out there could tell me if I require to get the spark plugs changed? i.e are they lifetime plugs? I think some of the new style Vectra's may have lifetime plugs, but I'm not sure. This is the most expensive part of the service and if I can do without changing them, it would be a bonus. Thanks