dukes dad,

Looking for better performance is why I would want to change from the stock plugs. With gas prices going up every little bit helps. Here is what Bosch has to say about their Platinum +4 plugs:

"Bosch guarantees that you will feel the improved performance in your vehicle when using the Platinum+4 Spark Plugs. If you do not experience quicker starts, smoother acceleration and improved fuel efficiency, simply return the plugs with your dated sales receipt and Bosch will refund the purchase price."