We lost the manaul to my wife's 2002 Focus. The car has 47k on it and it is getting very poor gas mileage. Not even close to what it should be. The airfilter was replaced. Not sure what else it could be. It doesn't have the ZTEC engine. Does anyone know if the PCV Valve or Fuel filters need to be replaced before 100k miles? Spark plugs? I'm trying to figure out what is the problem. This car has been through some rough winters and driving but the car just hasn' been as reliable as I would have hoped.