Learning how to replace the spark plugs on a Mazda RX8 yourself can save you a handful of money. There are four spark plugs to replace, two for the front rotor, and two for the rear. The design of the car makes this a somewhat daunting task to those who haven't tried it, but once you know how to do it, you'll never pay the dealer for a spark plug change again.
Jack up the car, and remove the driver's side front tire. Once the car is up, place a jack stand on the frame of the car, just in case the jack should fail.
Reach backward through the wheel well toward the back of the motor, and you'll feel the spark plug wires. Remove the wires by pulling on them.
Use the wrench to turn counterclockwise until the first spark plug is loose enough to turn by hand. When you remove the plugs, set them aside in a way that's easy to remember where they came from. The plugs are in a specific order, and have to remain that way.
Place a small dab of anti-seize to the threads of the spark plug, and screw them back into place. Take note of what the spark plug is marked with. All RX8 spark plugs are marked with a "T" or an "L." The "T" stands for trailing, while the "L" stands for leading. It's of great importance that these spark plugs go in the intended location.
Replace the spark plug wires by putting them over the plugs, and pushing down until they form a solid bond.
Behind the driver's side wheel, remove the bolt that secures the rubber splash guards in place. Once the bolt is removed, use a flathead screwdriver to remove the washer holding the guard on. Be gentle, as this is fragile. If it won't come off, give it a little twist.
Reach forward, toward the front of the motor and you'll be able to reach the front spark plugs. Remove the plugs and twist them with a wrench until they are loose enough to turn by hand.
Set the plugs aside in a way that allows you to remember where exactly each plug came from. Remember, the new plugs have to remain in the same order.
Place a dab of anti-seize on the new plugs and then insert the plugs into the holes created by removing the old ones. Take great care to put the plugs in the correct holes. Replace the plug wires.
Work in reverse order to reinstall the splash guard.
Mount the driver's side tire back onto the hub. Tighten the lug nuts.
It cannot be stressed enough that the new plugs have to go in the exact same spots that the old ones did. Each rotor has a leading and trailing plug, so it's important that you know which is which, so that you can replace them with the correct plug.