Spark plugs create the spark that ignites the air and fuel in each cylinder. They wear out gradually as the electrode erodes.
Why It Matters
Worn plugs cause misfires that damage the catalytic converter, a much more expensive part to replace.
How to Save Money on Spark Plug Replacement
Iridium plugs cost more upfront but last 80,000 to 100,000 miles vs 30,000 for copper
On 4-cylinder engines this is a very DIY-friendly job if you have basic tools
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