Spark plugs are simple, yet essential parts of your car engine's operation. They literally deliver spark to the ignition chamber to ignite the fuel. They receive power from the distributor, amplify it through heat, and ignite your engine's fuel.
Although these are simple devices, they are subject to wear from the fuel ignition and the carbon deposits that inevitably come with that. So they will eventually need replacement.
The interval for replacement of your spark plugs will depend on your vehicle. Older vehicles can require replacement as often as every 10,000 miles with most vehicles over 10 years old needing them about every 30,000 miles. Newer cars can have a much longer interval, being every 60,000 or more.
Check your manufacturer's recommendations and go with that. Anytime your engine seems to be sluggish, missing a cylinder, or otherwise in need of a tuneup, you probably need your spark plugs changed.
Costs of Replacement
The cost to change your spark plugs will depend on whether you do it yourself or pay a mechanic to do it. A few high-end vehicles may require special tools to replace the plugs, but most can be done by a home mechanic with just a little know-how. If you prefer to DIY, click here for instructions.
If you have a mechanic do it, the price will vary depending on the car, the number of plugs, and the cost of the plugs themselves. For most vehicles with 4 or 6 cylinders and as many plugs, a mechanic will likely charge in the $50 to $120 range. Smaller, more compact, front-wheel-drive cars are likely to cost more because it's harder to get to the plugs than a larger, easier to work with SUV or small pickup.
Some newer cars can be much more than that, getting in the $200 or more range. This is mainly due to the special tools and the high-cost spark plugs required for the vehicle.
For the DIY mechanic, spark plugs can be purchased at any automotive parts store for $2-$10 each on average. The newer, higher-end plugs that some cars may require can be twice or even three times that in some cases.
Regardless, your mechanic should be able to quote you a price for replacement up front, before any work is done. So always ask.