Owners of other Subaru vehicles such as the Forester, Impreza, Legacy, XV Crosstrek, WRX, BRZ, SVX, Tribeca, Exiga, Trezia, Levorg and Baja may also find these DIY instructions to be helpful.

The OEM spark plugs in this 2017 Subaru Outback were the laser iridium NGK SILZKAR7B11.

A few other compatible replacement spark plugs with their part numbers are as follows: Autolite XP5683, Denso (4712) IXEH22TT, Subaru 22401AA781 and Denso FXE22HR11.

The tools needed to remove and replace the spark plugs include a 10mm socket with a 1/4" drive ratchet, a 14mm spark plug socket or a 9/16" spark plug socket, a short extension bar, a 3/8" drive ratchet and a tube of dielectric grease.

Tip - Another Subaru owner let me know that using a piece of rubber hose or fuel line can make it much easier to get the new spark plug started. Just push the flexible rubber tube over the terminal (top of the spark plug) and use that to spin it in by hand. Then you can use the spark plug socket and ratchet to tighten the plug the rest of the way.

For easier access to the ignition coils and the spark plugs, you may choose to remove the engine air filter box on the passenger side and the 12V automotive battery on the driver side.

I chose to start on the passenger side of the engine. The procedure is the same for either side. If you don't remove the 12V battery, place a thick towel or mat over the top of the battery to help prevent accidental electrical contact.

The service manual specifies that the 12V battery should either be removed or you should disconnect the "-" negative (ground) cable from the battery.

Remove the single bolt that secures the ignition coil to the engine by turning it in the counterclockwise direction with a 10mm socket and a 1/4" drive ratchet.

For easier access to the ignition coils, I released the two metal latches on the air box to separate the two halves.

If you have trouble removing the ignition coil, try gently wiggling or rotating it back and forth while pulling it straight out.

Set the ignition coil aside in a safe place.

If you'd like to detach the electrical connector in order to replace the ignition coil, take a look at this image below. You can click on the small thumbnail image to view the full size picture.

Subaru FB25 - How To Disconnect Ignition Coil Electrical Connector

To remove the spark plugs, you can use either a 14mm spark plug socket or a 9/16" spark plug socket.

Attach the spark plug socket to a short extension bar.

Push the socket and extension bar into the spark plug well and securely attach it to the top of the spark plug.

Loosen the old spark plug by turning the ratchet in the counterclockwise direction.

Detach the old spark plug from the socket.

Inspect both sides of the old spark plug.

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

If the electrode tip of the old spark plug looks grey or is covered in dark black soot, the engine might be burning oil and should be inspected by a professional mechanic.

I recommend buying the genuine OEM NGK SILZKAR7B11 laser iridium spark plugs that are installed in the Outback at the factory.

If you have a spark plug gap gauge tool, verify that the gap on the new spark plugs match the specification on the product box. The service manual specifies that the standard plug gap is 0.039 to .0043" (inch) or 1.0mm to 1.1mm.

Push the new spark plug into the socket and insert it into the spark plug well.

Carefully spin the new spark plug in the clockwise direction by hand to prevent it from becoming cross threaded.

(If you do get your socket stuck in the spark plug well, just re-insert the extension bar, loosen the spark plug and fully remove it to recover the socket.)

Tighten the new spark plug in the clockwise direction.

If you are replacing the old spark plug after checking it, you only need to tighten it to a small fraction of a turn past finger tight.

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

If you have a very sensitive and reliable torque wrench, the service manual specification for tightening the spark plugs is 13.3 lb-ft (or 18 N-m).

Try to avoid over tightening the new spark plug to prevent from cracking it or damaging the threads.

Most spark plug manufacturers recommend that you do NOT use anti-seize lubricant grease on the threads of the new plugs since it can easily lead to over tightening of the spark plugs. If you do use anti-seize, be very careful to not over tighten the new spark plugs.

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

Push the ignition coil straight back into the spark plug well.

Tighten the ignition coil bolt in the clockwise direction with the 10mm socket and a 1/4" drive ratchet until it is snug.

The service manual specification for tightening the ignition coil bolt is 5.9 lb-ft (or 8.0 N-m).

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

Repeat the process to replace the two spark plugs on the driver side of the engine bay. Be sure to cover the 12 volt car battery terminals with a thick towel or a rubber mat to prevent yourself from being electrocuted.

Record the spark plug change in your vehicle's service records.

For more, please check out all of my 2015-2018 Subaru Outback DIY Repair & Maintenance Guides.