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Your vehicle’s spark plugs are components in a gasoline-powered, internal combustion engine that are essential to its proper function. Spark plugs are simple yet highly effective electrical devices that produce an electric ARC, igniting a fuel/air mixture within the combustion chamber. Essentially, spark plugs create a bolt of lightning detonating a fuel mixture inside a combustion chamber. 

In 1860, French engineer Etienne Lenoir was credited with inventing a spark plug. Several scientists had a hand in furthering the technology. However, Robert Bosch and Company was the first to create a functioning spark plug in 1901. His design was awarded a patent in 1902. 

  • Spark plugs consist of a terminal at the top, followed by the insulator (usually made of sintered aluminum oxide) preventing flashover. After the corrugated insulator is the HEX nut and threads. Spark plugs generally have copper cores leading to a center and side electrode or ground strap. Most plug designs have the center electrode in a cathode setup.
     

Spark plugs are all about design efficiency. Spark timing, electrical field strength, and electron emissions are keys to the engine’s performance. Any reputable dealer, auto or engine mechanic, and knowledgeable grease monkey knows when to check and replace spark plugs. 

How Long Do Spark Plugs Last?

One of the great aspects of modern vehicle technology is that everything seems to be getting smaller and lasting longer. Spark plugs are engine components that can foul after a few months of use or last a lifetime. Mechanics agree spark plugs need to be checked or replaced with every scheduled maintenance, depending on how hard the vehicle is used.

The perfect place to start researching your vehicle is a GoodCar Vehicle History Report. This essential online summary describes vital information on the history of your vehicle, such as odometer readings, accident history, title (salvage/junk), and details on the vehicle’s build. 

The owner’s manual is the best place to find information on scheduled engine maintenance. If your car or truck does not have a manual, look to the internet. Every manufacturer has a support site for legacy models, or you could purchase a manual from sites like eBay and Edmunds.

What Causes A Spark Plug To Fail?

What Causes A Spark Plug To Fail?

Spark plugs are generally a wear-and-tear type of engine component rather than an all-at-once disaster part. There are definitive signs a driver needs to be aware of when out motoring. Over time, spark plugs become less efficient, causing rough idle, reduced acceleration, and poor gas mileage.

It is rare for a spark plug to go bad early. (before the first scheduled maintenance check) The most common signal would be a problem with the ignition system, lengthy low-speed driving, or extended idling periods.

Drivers will notice several signs when to replace spark plugs in their vehicle:

  • Overheating wreaks havoc on every engine component, especially the spark plugs. Combustion engines and spark plugs generate large amounts of continued, enclosed heat. Engine and spark plug overheating can be caused by a part failure (radiator leak) or lack of exhaust ventilation. Metallic plugs generate significant amounts of heat through a build-up of fractured iron and carbon deposits.
  • Carbon build-up on the center and side electrodes causes a host of engine problems and plug failures. Dirty air filters, excessive low-speed driving, and dirty fuel injectors may cause carbon-fouled plugs. Maintaining your vehicle with a knowledgeable mechanic saves a lot of future headaches. Good mechanics always double-check the electrode gap on the spark plugs they install. Incorrect gaps contribute to high rates of misfiring, engine start-up trouble, and other problems.

 

How to Clean Spark Plugs

Begin by visually inspecting your spark plugs for any major damage or wear. If they are cracked, excessively fouled, or the electrodes are worn down, they will need replacement rather than cleaning.

  • Remove Spark Plugs: Using a spark plug socket and ratchet, carefully remove the spark plugs from the engine. It's essential to do this gently to avoid damage to the threads.
  • Brush off Loose Debris: Use a wire brush to gently scrub off any loose debris or carbon build-up from the plug. This step is crucial for removing surface-level dirt without damaging the plug.
  • Apply Cleaning Solution: For a deeper clean, use a commercial spark plug cleaner or a mixture of household cleaning agents (like vinegar or baking soda solution). Submerge the spark plug in the solution and let it soak for several minutes.
  • Scrub and Rinse: After soaking, scrub the plug again with the wire brush to remove any remaining deposits. Then, rinse the plug thoroughly with clean water.
  • Dry the Spark Plug: Before reinstallation, ensure the spark plug is completely dry. You can air dry it or use a clean cloth to wipe it down.
  • Check and Adjust Gap: Ensure the gap between the spark plug's electrodes is correct for your vehicle. This can be adjusted using a spark plug gap tool.
  • Reinstall Spark Plugs: Carefully screw the spark plugs back into their sockets. Ensure they are snug but do not over-tighten, as this can damage the threads.
  • Test Your Engine: Start your engine to ensure that it's running smoothly. Any misfires or unusual noises may indicate that the spark plugs are not properly cleaned or installed.
     

Regular cleaning of your spark plugs can improve engine performance and fuel efficiency. However, it's important to recognize when cleaning is insufficient and replacement is necessary.

Cost To Change Spark Plugs  

Maintaining a well-running car or truck is a matter of constant upkeep, using the right type of oil or gas, and a good mechanic. Rather than every once in a while and always using the cheapest gas and oil.

Every manufacturer, dealer, and knowledgeable mechanic have their opinion on when to inspect and replace spark plugs. To maintain peak performance, it is recommended to replace plugs every 30,000 miles. However, refer to the tips above if your vehicle shows signs of rough performance.

Most vehicle manufacturers go by a 30/60/90k-mile maintenance schedule. These major service checks are designed to inspect, change out, or replace specific items throughout the vehicle. Minor servicing is performed at 7,500, 15,000, and 45,000. Each interval should include essential car maintenance, oil and filter change, replace transmission fluid, tire rotation, and of course, wear and tear of the spark plugs.

High-quality, premium spark plugs meet most OEM specifications, hold their shape for much longer, and provide excellent long-term performance characteristics.

Spark plug technology has skyrocketed over the years, with producers crafting center electrodes of iridium and platinum with higher melting points, resulting in slower erosion. At present, iridium is the premier element in center electrode spark plugs, offering a more powerful spark at higher temperatures.

How Much Is It To Replace Spark Plugs?

The average cost of a copper spark plug is $2 to $10 each, while platinum and Iridium plugs range from $8 to $15 apiece. If you are sitting down, aircraft, racing, and high-performance spark plugs can reach $80 to $200 apiece and more.

Labor charges will always vary, depending on the shop or service lane and location you choose. V8 and V6 engines will generally cost more to maintain than a V4 or single-cylinder engine. According to J.D. Power, the average cost for spark plug replacement, factoring in parts and labor, is somewhere between $100 and $250. The highest average price is between $250 and $500.

Keep Your Spark Plugs Fully Functional

There are a lot of motorists on the road who never follow hard and fast rules of maintaining their vehicle for peak performance. Stubborn drivers may forget or refuse to replace worn or bad spark plugs, even though the signs are right in front of them. Carbon deposits can build up on the electrodes of a plug, causing severe misfires and sluggish performance. Unburned fuel in the cylinder eats away at the cylinder walls, and dangerous pressure levels build up inside the combustion chamber. These extreme circumstances may lead to a complete engine failure. 

New engine replacement costs average upwards of $4,000 to $10,000 depending on make and model.

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