What are Car Spark Plugs?


In order for a car to begin operating and moving, it must have a spark plug, which is an essential component. The spark plug is a device that is installed in an automobile’s engine and is primarily used to generate a spark and ignite the air-fuel mixture within the engine’s combustion chamber, thereby allowing the fuel and engine to produce energy to move the car’s other components. How does a spark electrode operate? We will find out as we examine spark plugs and their significance for automobiles and other types of vehicles.

Types of Spark Plugs 

Copper Core Spark Plugs

Copper spark plugs are the most commonly used because they are the least expensive. The outer material of copper spark plugs is nickel-alloy, which wears down quickly due to the engine’s cylinder’s high pressure and high temperature. This attrition causes fouling of the spark plugs; consequently, their lifespan is reduced.

Copper connectors with a solid copper core and a nickel alloy electrode have existed for more than a century. Since nickel is weaker than platinum or iridium, its lifespan is significantly shorter. Typically, these connectors are optimal for older, low-voltage systems. Copper’s high conductivity necessitates their use in some high-performance vehicles.

Iridium Spark Plugs

Iridium plugs, which are harder than platinum, were introduced to the market in the mid-2000s as coil-on-plug systems gained popularity. Iridium spark plugs typically have the smallest center diameter, which can increase efficacy by decreasing the voltage required to create a spark. Iridium is also renowned for its ability to continue firing under extreme conditions. If your manual specifies iridium spark plugs, the best course of action for optimal performance is to endure the additional cost associated with this rarer metal.

Iridium has a higher melting point and is more durable than platinum, giving it superior wear properties. In addition, iridium spark plugs have a thin wire center electrode that conducts electrical energy more efficiently and improves firing efficacy. Due to these characteristics, iridium spark plugs have a longer lifespan than platinum spark plugs.

Platinum Spark Plugs

In the late 1980s, when ignition systems began to migrate from distributor-based systems to coil pack or DIS (wasted spark) systems, a connector capable of withstanding the higher-energy, more demanding system was required. Manufacturers made a concerted effort to develop spark plugs and refrigerant with a lifespan of 80-100,000 miles or more, which increased the durability of the harder, platinum material. Platinum plugs utilize a platinum disc that is welded to the end of the center electrode. This enables the plug to last longer than a copper plug by retaining its edge more effectively, resulting in greater conductivity. Platinum spark plugs tend to operate at a higher temperature, preventing fouling and deposit accumulation. 

The melting point of platinum is greater than that of nickel alloy. Additionally, it is harder, which is why it retains its keen edge longer than the copper spark plug. In addition, it is resistant to high temperatures, which increases the spark plug’s overall lifespan. There are two types of platinum spark plugs: single platinum spark plugs and double platinum spark plugs.

How Spark Plugs Work 

spark plugs installed into a car engine

Modern spark plugs have a copper center electrode surrounded by a nickel alloy, which is visible at the point of the spark plug. Inside the spark plug, the center electrode is encased in porcelain, which facilitates the transmission of engine heat to the cooling system. Premium spark plugs replace the nickel alloy with precious metals such as platinum or iridium. These metals have higher melting points and correspondingly higher prices.

The spark electrodes are situated atop the cylinder head. The piston descends the cylinder as it draws in a mixture of air and fuel. The piston then returns to the spark electrode, where it compresses the mixture. When the piston is at top dead center, the ignition coil sends voltage to the spark electrode, igniting the air/fuel mixture and producing a spark. The piston then returns to its original position, generating propulsion for the vehicle. The piston then returns to the top and expels the exhaust on its ascent. At this juncture, the entire procedure begins again. This combustion event provides your vehicle with the necessary power to operate.

Regarding temperature, spark plugs are available in two primary varieties: cold and hot. Cold spark plugs are most effective in high-horsepower, high-compression engines. They have less insulation, allowing for greater heat transfer from the combustion chamber to the engine’s exterior. If the plug is not frigid enough for a specific application, it cannot remove enough heat from the piston chamber. This may result in premature ignition, clanging, and irreparable engine damage. If you are unsure of which spark plug thermal range to use, use a spark plug that is too cold rather than one that is too hot.

Hot spark plugs have greater insulation and are present in the majority of standard engines. Extra insulation maintains the plug’s temperature at a level sufficient to burn off carbon deposits, extending the time between spark plug replacements.

To ignite the mixture of oxygen and fuel. If the voltage supplied to the spark plug is high enough, electrical energy is transmitted through it, bridging the crevice in the plug’s firing end. This spark ignites the mixture of gasoline and oxygen in the combustion chamber. To evacuate heat from the chamber of combustion. Spark plugs cannot generate heat, only dissipate it. The combustion end of the plug must be kept at a temperature low enough to prevent pre-ignition, but high enough to prevent fouling. The spark plug functions as a heat exchanger by transferring undesirable thermal energy from the combustion chamber to the cooling system. Heat range is the capacity of a spark plug to dissipate heat from its tip.

Replacing Spark Plugs 

used spark plugs

Spark plugs are designed for long-term durability, so they need to be replaced every 80,000 to 100,000 miles at most. However, they can be damaged sooner than anticipated and must be replaced to prevent expensive engine repairs.

Keep in mind that your spark plugs are four fifths worn after 80,000 miles. The space between each spark electrode will continue to grow, diminishing fuel economy and engine performance. In order to monitor their condition, we recommend servicing your spark plugs every 30,000 miles.

Steps for Replacing Spark Plugs 

1. Safety comes first

Place your vehicle on a level, dry surface and make certain the engine is cold. To prevent anything from falling into the engine cylinder during spark plug replacement, thoroughly clean the engine area. Additionally, the battery may need to be disconnected. Check the vehicle repair manual or other resources to ensure that disconnecting the battery for any length of time will not cause any damage or that any modules or other components will need to be reprogrammed. Ensure that the positive and negative terminals are not crossed by a foreign object, such as a hand ratchet, which could result in a hazardous short circuit.

2. Identify your spark plugs

The spark electrodes on a four-cylinder engine may be located on the side or the top of the engine head. Moreover, spark electrodes are evenly spaced on both sides of V6- and V8-cylinder engines.

The owner’s manual for your vehicle will explain where the spark plugs are and how many you need. Most automobiles have four to twelve spark plugs. There is typically one spark electrode per cylinder, although some models use two per cylinder. In either case, it is essential to replace all of the connections at the same time, as identical electrical resistance levels ensure optimal performance.

3. The coil on plug (COP) should be removed

COP coils utilize a long rubber insulator boot and adhere directly to the spark plug end. Start the removal procedure by disconnecting the ignition coil’s electrical connector. The connector can be disconnected by pressing down or pulling up on the locking tab. It may be necessary to use a small screwdriver to depress the securing tab. Once the connector is removed, remove the hold-down bolt and twist the coil back and forth a quarter turn or so until the ‘bond’ is severed. Then it should draw directly upward and outward. Use prudence! There is always a chance that the COP footwear will be damaged. 

4. Remove the outdated spark leads

Using an extension and adapter set for spark plugs, remove each spark plug individually. Hold each plug as close to its base as possible and revolve it counterclockwise until it becomes loose. Caution should be taken not to pull too forcefully, as doing so could damage the spark plug leads. It is crucial that you replace your spark plugs if there is any white buildup around the electrodes, if any portions of the electrodes have worn away, or if there is evidence of burning.

5. Grease the new spark plugs

Apply a small quantity of anti-seize lubricant to your new spark plugs to prevent them from sticking the next time you need to replace or inspect them. This lubricant can also prevent metals from reacting with one another.

6. Insert the replacement spark plugs

As you tighten your spark plugs, you may wish to slip a brief length of rubber hose over the plugs to increase grip.

Insert the wire end of each spark plug and manually tighten each one. If you have a torque wrench, you can properly torque your spark plugs; the torque specification for your model can be found in the owner’s manual.

Ensure that the new spark plugs are connected to their original wires – spark plugs ignite in a specific order, and mismatched wires can prevent the engine from operating properly and potentially cause irreparable damage.

7. Start the vehicle

Starting the engine after replacing the spark plugs is a good method to verify your work. If your Check Engine Light is illuminated, you can still drive your car. If the Check Engine Light ‘flashes’, a cylinder misfire is present. Check your work again. If the engine is absent, do not drive the vehicle very far because the catalytic converter could be damaged.

Before installing your spark plugs, you may need to adjust the separation. Some connections are pre-gapped, and the packaging will indicate this if this is the case. Otherwise, you will need a gap tool to properly space your new connectors according to the owner’s manual. You may only need to replace spark plugs once or twice during the time you own a vehicle, as most modern automobiles use spark plugs made of durable materials.

Tools Required for Spark Plug Replacement

  • Ratcheting socket wrench
  • Socket wrench extension
  • Spark plug socket
  • Flexible socket wrench joint adapter, if necessary
  • Spark plug gap tool
  • Torque wrench
  • Vacuum and/or compressed air blower
  • Clean rag or paper towels


Replacing your spark plugs ensures a consistent combustion spark, ensuring that your car will start reliably and that your fuel economy will remain optimal. Spark plugs ignite the fuel in gasoline-powered vehicles, but their lifespan is limited. They deteriorate over time and should be replaced as part of your maintenance plan. Once you have the proper equipment, changing your spark plugs is a simple task that can be completed in less than an hour in order to avoid expensive auto service fees.

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