Corvette Spark Plugs (Set) - NGK Iridium IX : 1992-1996 C4Corvette Spark Plugs (Set) Iridium IX : 1992 1996 C4 GM recommends checking and if necessary replacing your spark plugs every 35,000 miles. Price is for a set of (8) plugs. These NGK Iridium IX spark plugs feature an ultra fine center electrode that's designed just thick enough to ensure the maximum durability and life of the spark plugs, and just thin enough to create an accurate and consistent spark. They represent the ultimate evolution of spark