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Mazda Mazda6 Spark Plugs Replacement Guide
How to change the spark plugs in a 3rd generation 2014 to 2018 Mazda 6 sedan with the SkyActiv-G 2.5L I4 motor.

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2016 Mazda 6 2.5L I4
Lift Off Engine Cover
Plastic Cover Removed
This automotive maintenance tutorial was specifically written to assist owners of the third generation (2014, 2015, 2016, 2017 and 2018) Mazda Mazda6 sedan in checking or changing the engine spark plugs in the SkyActiv-G DOHC 16V VVT 2.5 liter inline four cylinder motor.

Owners of other Mazda vehicles such as the Mazda2, Mazda3, Mazda5, CX-3, CX-5, CX-7, CX-9, and the MX-5 Miata may also find these DIY instructions to be helpful.

The OEM iridium tipped spark plugs in this 2016 Mazda 6 were part number NGK ILKAR7L-11 (also known as, ILKAR7L11 (94124), ILKAR7L 11 and Mazda PE5R18110 or PE5R-18110.)

A few compatible replacement spark plugs with their part numbers are as follows: Denso (4711) IXEH20TT, Bosch (9621) VR7NII33X, Pulstar GG1H10, Autolite XP5682 and Champion Iridium 9412.

The tools and other items needed to complete this procedure include an 8mm socket, a 1/4" drive ratchet, a 14mm spark plug socket (or a 9/16" spark plug socket), a set of extension bars, a 3/8" drive ratchet and a tube of dielectric grease.

Clean Top of Engine
Spark Plug Ignition Coil
Push Down Release Tab
The first two steps are to open the hood and then gently pull off the plastic engine cover.

The engine cover is only held in place by a few rubber friction fasteners. Set the engine cover aside in a safe place.

If you have access to compressed air or a wet/dry shop vacuum, thoroughly clean off the top of the engine to help reduce the change of having debris fall down in to the spark plug well.

Press the release button on the electrical connector and slide it straight off the ignition coil. If you have trouble removing the power plug, you may need to use a flathead screwdriver to firmly press down the release tab.

I'd recommend only checking or changing one spark plug at a time to help further reduce the risk of dropping something in to the cylinder head.

Disconnect Power Plug
Loosen Counterclockwise
Remove 8mm Bolt
Remove the single bolt holding the ignition coil housing in place to the top of the engine by turning it counterclockwise with an 8mm socket and a 1/4" drive ratchet.

Set the bolt aside in a safe place.

Rotate Back & Forth
Lift Out Ignition Coil
Spark Plug Well
Rotate the ignition coil back and forth a few times to make sure the rubber dust boot is not stuck or "frozen" to the top of the old spark plug.

Lift the ignition coil assembly straight out of the spark plug well and set it aside in a safe place.

14mm Spark Plug Socket
Loosen Counterclockwise
Detach Wrench - Spin Out
Attach the 14mm spark plug socket to a 6" extension bar and the 3/8" drive ratchet.

(A 9/16" spark plug socket would also work.)

Lower the socket down in to the well and attach it to the top of the old spark plug.

Loosen the old spark plug by turning it counterclockwise.

If you have trouble loosening the old spark plug, try spraying in a small amount of penetrating oil such as PB Blaster, Liquid Wrench or Kano Kroil and wait 15-30 minutes or more before trying again. If you don't have any penetrating oil, try spraying in some WD-40 or just warm up the engine for a few minutes to expand the metal engine block.

Once the old spark plug is loose, detach the ratcheting wrench and spin it out the rest of the way by hand.


Lift Out Old Spark Plug
Inspect Old Spark Plug
Spin In New Spark Plug
Lift the old spark plug out of the well and detach it from the socket.

The OEM spark plugs in this 2016 Mazda 6 were part number NGK Iridium (94124) ILKAR7L11 (also known as Mazda PE5R 18110).

Inspect both ends of the old spark plug.

If the electrode end of the old spark plug looks ashy white, the plugs might have been exposed to high temperatures such as engine overheating or they are the incorrect heat range for your driving conditions and/or environment.

If the old spark plugs are dark grey or covered in black soot, the engine might be burning oil and should be checked by a professional mechanic.

If you have a spark plug gap gauge, check the gap on the new spark plugs to ensure that they match the manufacturer's specifications on the box. The OEM iridium NGK ILKAR7L-11 plugs should be gapped to 0.044".

Push the new spark plug in to the socket and lower it down in to the well.

Spin the new spark plug in the clockwise direction by hand until it makes contact with the top of the cylinder head.

Tighten Clockwise
Apply Dielectric Grease
Lower In Ignition Coil
Attach the 3/8" drive ratchet to the extension bar.

Tighten the spark plug in the clockwise direction to just past the point when you feel the new crush washer collapse.

If you are re-installing the old spark plugs, tighten the old spark plug to a fraction of a turn until it is snug.

Try to avoid over tightening the spark plugs to prevent from cracking the ceramic portion of the plug or damaging the threads.

If you have a very sensitive and reliable torque wrench, the service manual lists a spark plug torque specification of 12 to 14 lb-ft (or 15 to 20 N-m).

Apply a small amount of dielectric grease to the opening at the bottom of the rubber dust boot.

The dielectric grease will help keep out any moisture or debris to ensure a reliable electrical connection.

Lower the ignition coil in to the spark plug well.

Rotate Back & Forth
Re-Insert 8mm Bolt
Tighten Clockwise
Rotate the ignition coil housing back and forth a few times to help spread the dielectric grease.

Re-insert the 8mm bolt and tighten it in the clockwise direction until it is snug.

Try to avoid over tightening the 8mm bolt to prevent from cracking the plastic ignition coil housing.

Push On Electrical Connector
Line Up Friction Fasteners
Engine Cover Replaced
Push the power plug straight on to the ignition coil housing until it clicks securely in to place.

Line up the pegs and rubber friction fasteners on the underside of the engine with their corresponding points on the top of the engine.

Push the engine cover back in to place.

Start the engine and listen closely for any strange noises that might indicate a problem such as a disconnected electrical connector or a loose spark plug.

Be sure to record the spark plug change in your car's service records.

For more, check out my other 2014-2018 Mazda Mazda6 DIY Repair & Maintenance Guides.

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