ACDelco Professional Conventional Spark Plugs are designed for reliability and efficient performance, and are the high quality replacement ideal for many vehicles on the road today. Their high-quality copper cores and outstanding suppression characteristics deliver reliable performance. They are also available for Marine applications. These premium aftermarket replacement spark plugs are manufactured to meet your expectations for fit, form, and function.


  • Black Onyx coating helps reduce corrosion
  • Copper core provides great heat transfer and helps maximize plug durability
  • Ribbed suppressor seal extends resistance and helps prevent spark "flash over" and misfires
  • Nickel-chrome alloy sheathing helps prevent corrosion on the center electrode.
  • Available for use in Marine applications


Signs of wear for professional conventional spark plugs include but are not limited to:

  • Your engine has trouble starting, or is hesitating, or cutting out
  • Sluggish engine performance, loss of engine power, or decreased fuel economy
  • Lack of acceleration or loss of speed when driving uphill under load
  • Cracks in the upper or lower portion of the spark plug insulator
  • Chipped or broken insulator tips
  • Damaged spark plug boots


Visually inspect spark plugs for signs of wear. Follow these steps to remove spark plugs for inspection, servicing, or replacement:

  • Grasp the spark plug boot and gently rotate it 90 degrees counterclockwise. Pull the spark plug boot and cable away from the spark plug. If necessary, use a spark plug boot removing tool. DO NOT grab or violently pull spark plug cables. 
  • Brush or air blast dirt away from the well areas before removing spark plugs. CAUTION: Use goggles to protect eyes from debris when applying compressed air to spark plug wells.
  • Use the correct deep socket size to loosen each spark plug one or two turns. NOTE: To remove spark plugs from aluminum heads, allow the engine to cool. The heat of the engine, in combination with a spark plug that is still hot, may cause the spark plug threads to strip the cylinder head upon removal.
  • Remove each spark plug and place each one in a tray by cylinder number. This will help identify and relate any unusual condition to the cylinder involved. 
  • Apply dielectric grease into the boot area to reduce the chance of exterior tracking on the buttress tower of the spark plug. This grease also promotes a good heat transfer between the spark terminal screw and boot terminal. 
  • Before installing new spark plugs, use a gap guide to make sure your new spark plugs have the correct gap. 
  • Install spark plugs or glow plugs to the proper torque per the manufacturers’ specification.


Q: Is there a recommended interval for changing my vehicle’s spark plugs? 
A: Yes, this interval depends on what type of spark plug your vehicle requires. Refer to your owner’s manual or contact your vehicle’s manufacturer for more information.


Q: Should I change all of my vehicle’s spark plugs at the same time? 
A: Yes, if it is the scheduled time for spark plug replacement. It is okay to replace one spark plug if it is fouled or damaged prior to scheduled maintenance, provided the source of the damage is found and corrected.


Q: Does a diesel engine require a different type of plug than a gas engine? 
A: Yes. Diesel engines require glow plugs because diesel engines operate differently than gas engines. ACDelco Professional Glow Plugs are specially designed to give diesel engines the heat they need for their cold starts. Refer to your owner’s manual or contact your vehicle’s manufacturer for more information.


Q: Are ACDelco spark plugs pre-gapped? 
A: Yes. When ACDelco spark plugs are manufactured, they are pre-gapped to the correct gap specification.


Q: When I replace my spark plugs, should I also replace my spark plug wires? 
A: Not always, but you should inspect your spark plug wires for wear when replacing your spark plugs. Refer to your vehicle owner’s manual or contact the manufacturer for more information.


Q: What is pre-ignition and can it damage my engine? 
A: Yes, pre-ignition can cause serious damage to your engine. Pre-ignition is the ignition of fuel before the actual spark occurs, which causes a rapid temperature rise in the combustion chamber that can damage engine components and melt spark plug electrodes. Causes of pre-ignition include but are not limited to a buildup of deposits that can become incandescent in the combustion chamber, improper installation torque being applied to spark plugs, and having spark plugs with a heat range that is too hot for the engine’s operating condition.  


Q: Can I just clean my spark plugs instead of replacing them? 
A: No, cleaning your old spark plugs is not recommended. Dirty, fouled spark plugs may also have broken or chipped insulator tips, worn electrodes, or worn or missing side wires. These conditions severely affect spark plug performance. Replace your dirty, fouled spark plugs with new ACDelco spark plugs.