We guarantee your satisfaction or the improved performance in your vehicle when you use Bosch Iridium Spark Plugs. If you are not satisfied or do not experience quicker starts and smoother acceleration, return the plugs with your dated sales receipt and Bosch will refund the purchase price of the spark plugs.
This guarantee applies to properly tuned vehicles and extends for seven years, or for the manufacturer's recommended spark plug change interval as indicated in the owner's manual.