Better Gas Mileage: How to Change the Spark Plugs in Your Car
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Better Gas Mileage: How to Change the Spark Plugs in Your Car

The reader will learn how to change spark plugs correctly.

Change your own Spark Plugs!

If you own a vehicle, it is beneficial to know how and when  to change your own spark plugs.  Spark plugs provide the electric spark that ignites the gasoline in your engine. To have plugs dirty, worn, or defective is an invitation to poor gas mileage and bad engine performance.  If you know how to change spark plugs, you can help keep your engine running at its best, get better gas milage, and save money too.

When should you change spark plugs?

If your motor is starting poorly, running roughly, and getting poor gas mileage, it is likely your spark plugs should be changed. Accumulations of solids in the plugs collect from unburned fuel, burned oil, dirt, and other contaminants. Like any other mechanical device, a spark plug can eventually wear down. Worn or corroded electrodes on spark plugs create a weak, inefficient spark. Perhaps the ceramic insulator on the plug is cracked, allowing moisture to drain power from the plug as it fires, resulting in a weak, inefficient  spark.

To change spark plugs, you will need:

• A new set of spark plugs for your vehicle. Refer to the owner’s manual or automotive parts supplier lists to obtain the correct type, size, and heat range for your vehicle.

• A spark plug wrench or spark plug socket of the correct size with a ratchet and short extension. For some vehicles that are poorly designed, a special tool may be required. Borrow if necessary.

• A pair of pliers or “a plug boot remover” to remove the spark plug cover and boot if applicable. Use the right tool to avoid crushing the brass terminal in the end of the wire.

• A spark plug gapping tool/ feeler gauge.  Specifications for spark plug gap will be found in your owner’s manual settings section.

Follow this handy method to change Spark plugs:

• Park the vehicle on a level, flat surface. Place the transmission in Park, set the parking brake, shut off the ignition and remove the keys from the ignition.

• Remove the cable from the positive (+) battery terminal. 

• Pull the rubber boots from the spark plug carefully, using the plug boot remover or pliers. Twisting the rubber boot carefully back and forth just a bit can help if the rubber boot seems to be stuck.  Do not twist it continuously  around in one direction, as you may damage the wire.

• Install the spark plug socket, carefully inserting it over the spark plug. Turn it counter-clockwise and remove the plug carefully. Twisting the wrench at the wrong angle can break off a spark plug, so carefully observe the angle at which the plugs sit!

• Clean the seat of the spark plug, and remove any dirt accumulation.

• Check the new spark plug for the correct gap and set or adjust it as necessary.

• Insert the new plug into the engine. Start threading it in using only your fingers or the socket and a short extension, without using the ratchet, to ensure the plug is not cross-threaded. If it jams, it is cross threaded. Do not force it, but remove it and try again.

• Tighten the new plug to the specified tightness. Do not over-tighten spark plugs!.

• Check the plug wire for cracks, and reinstall it, seating it firmly on the plug.

• Reinstall the plug cover if applicable.

• Install all remaining spark plugs using the same technique.  Make sure you replace each wire on the the correct plug!

• Reinstall the positive (+) battery cable.

• Start the engine and ensure it is running correctly.

Now you know how to change spark plugs!  You have not only saved money changing your own spark plugs, but you  will experience better engine performance and save money on gasoline too!  Simple, wasn’t it?

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Comments (3)

thanks for the tips.

This is a good article except for one thing, you should always remove the battery's ground (-) cable first, never the positive (+) cable. There is a very good reason for this--safety. Your safety and your vehicles safety. You never remove the positive cable first because if your wrench was to make contact with the car's body, or some other metal part under the hood during the process, a short circuit would occur which could destroy on-board electronic components and possibly cause the battery to explode. Such a rapid discharge of the battery could also cause serious burns to your hands. Two other things. On newer cars you will need to plug a "Battery Keeper" into the cigarette lighter socket, before disconnecting the battery to protect the programming of the vehicle's on-board computers. Failure to do this can cause irreparable damage to the computer. A "Battery Keeper" is nothing more than a device with a 9-volt battery in it and can be purchased at most auto prats stores for less than $10. It is also a good idea to coat the threads on the new spark plugs with an anti-seize compounds before installing them. This will make it easier to remove them the next time you want to remove one or more of them.

Jerry, thank you for bringing up that excellent point regarding the removal of the battery cables. Disconnecting the positive cable first does remove the source of power to all circuits, but doing it first carelessly most certainly will cause arcing if your wrench does happen to touch metal parts. It is safer to remove the ground negative cable first. As modern vehicles have ever-increasing numbers of electronic and computer components, it is indeed a bad idea to allow any short-circuits or arcing in the automotive system. If the battery must be replaced , the computer systems should "boot up" to the default settings and function correctly if there has been no damage done to the system. I must agree it is also a good idea to use anti-seize compound on the threads of spark plugs, but should be used minimally to avoid excessive compound entering the combustion chamber. Thank you for taking the time to comment, much appreciated! posted 10 minutes ago