Owners of other Mitsubishi vehicles such as the Mirage, Lancer Evolution ("Evo"), Outlander, 3000GT, Diamante, Eclipse, Endeavor, Galant, Montero, ASX, Triton L200 and Raider may also find these DIY instructions to be helpful.

The OEM spark plugs in this 2015 Lancer were the NGK Iridium # DIFR6C-11 or "DIFR6C11".

The tools needed to complete this procedure include a 10mm socket with a 1/4" drive ratchet, a 5/8" spark plug socket, a 6" extension bar, a 3/8" drive ratchet and a tube of dielectric grease.

A few compatible replacement spark plugs for the MIVEC 2.0L I4 engine (naturally aspirated) with their part numbers include the following: Denso (4504) PK20TT, ACDelco 41-801, Autolite AP3923DP2 and Champion 3344.

Replacement spark plugs for the MIVEC 2.4L I4 engine with their part numbers include the following: Autolite APP3924, Denso (5303) IK16, NGK DIFR5C11 and the Champion RC12PMPB4 (7318).

Loosen the three bolts on the access panel by turning them counterclockwise with the 10mm socket and 1/4" drive ratcheting wrench.

Set the three bolts aside in a safe place.

Lift the plastic cover straight off the top of the engine.

Loosen the single bolt holding the ignition coil in place by turning it counterclockwise with the 10mm socket and ratcheting wrench.

Rotate the ignition coil back and forth a few times to make sure that the rubber dust boot at the end is not stuck to the top of the old spark plug.

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

Lower the socket down over the top of the old spark plug.

Then carefully loosen the old spark plug by rotating the wrench in the counterclockwise direction.

Try to avoid using excessive force to loosen the old spark plug to prevent from cracking the ceramic portion of the plug.

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

Once the spark plug has been loosened, detach the ratcheting wrench from the extension bar and spin it out the rest of the way by hand.

Carefully lift the extension bar and the old spark plug out of the well.

Pull the old spark plug out of the socket and inspect it.

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

On the other hand, if the old spark plug is grey or covered in dark black soot, the engine may be burning oil and should be examined by a professional mechanic.

I recommend buying the Denso (4504) PK20TT spark plugs since they have excellent reviews on Amazon.

(An optional step is to apply some anti-seize grease to the threads on the spark plug. Most spark plug manufacturers recommend that you should not use anti-seize grease since it can lead to over tightening. Some mechanics believe that using anti-seize grease on the spark plugs will help prevent them from becoming stuck or "frozen" in to the cylinder head if they are not removed again for 100,000 miles.)

If you have a spark plug gap gauge, check that the new spark plugs are gapped to the manufacturer's specification listed on the box. They should be pre-set from the factory, so don't worry if you don't have a gap gauge.

Push the new plug in to the 5/8" spark plug socket. Your socket should have a rubber insert or a strong magnet to ensure that the new spark plug remains in place.

Carefully lower the spark plug down in to the well and spin it in by hand in the clockwise direction until it makes contact with the cylinder head.

Attach the 3/8" drive ratcheting wrench to the extension bar and continue tightening the spark plug in the clockwise direction.

If you are re-installing the old spark plug, tighten it to just a small fraction of a turn past hand tight.

If you are installing a brand new spark plug, tighten it to just past the point when you feel the new crush washer collapse.

Do not over tighten the spark plug to prevent from cracking the ceramic body or stripping the aluminum threads.

Double check that the new spark plug is tight before moving on to the next steps.

The dielectric grease will help keep out any moisture and prevent corrosion from forming.

Rotate the ignition coil back and forth a few times to help spread the dielectric grease.

Spin in the 10mm bolt by hand.

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

Push the electrical connector straight on to the base of the ignition coil until it clicks securely in to place.

Lower the spark plug access cover back in to place on the top of the engine.

Spin in the three 10mm bolts by hand a few turns in the clockwise direction to prevent from becoming cross threaded.

Tighten the 3 bolts in the clockwise direction with the 10mm socket and ratcheting wrench until they are snug.

Start the engine and listen closely for any strange sounds that may indicate a problem such as a disconnected power plug or a loose spark plug.

For more, check out my other 2008-2015 Mitsubishi Lancer DIY Repair & Maintenance Guides.