99 Continental. Owners manual says 5000 miles or 6 months, whichever comes first. I've been religious about changing every 3000 miles or 3 months, whichever came first. Am I doing an overkill on this? It would be nice to save the money by going the 5k/6mo route, any strong opinions? Using Motorcraft synthetic and motorcraft filter, should I be using something else? Thanks, Bill.