Is there a writeup to replace the spark plugs on 5th generation? All I can find is 4th gen and I dont know if there are any differences. Also, what is model of NGK spark plugs to use? Search has not really helped me as all I can find it for older generations.
Spark plug DIY?
nappyjim
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2012 Subaru Outback 2.5i AWD (4 Cylinders 2.5L FI SOHC 150 CID)
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163 Posts
Did my brothers 2016 2.5 with 102K miles a few days ago... he had never had the plugs changed. Yeah, agree totally on the over-engineered 14mm horizontal bolts on the battery tray. I may or may not have only reinstalled 5 of the 6 bolts and not the bottom 14mm one 
...I definitely needed the 14mm flex-head ratcheting box end wrench. Ended up needing to make it longer by duct-taping a long screwdriver to the side of it. The other tip that helped was using a flexible head magnet (see attached photo). That totally saved me when I dropped a couple of bolts down into the abyss... also one of the small metal clips that goes onto the ignition coil. Would have been a major PITA to take off the plastic protector under the car to find it, but instead, all I had to do was go fishing with my flexible head magnet and move it around under the engine and it picked up those bolts and metal clips immediately. Also, having done my 2012 2.5 OB 60K miles ago, when it was at 100K miles, looks like it's time to do it again. After the major PITA that the 2016 OB was, I can't wait to do it on the 2012 again, it was sooooo much easier.
...I definitely needed the 14mm flex-head ratcheting box end wrench. Ended up needing to make it longer by duct-taping a long screwdriver to the side of it. The other tip that helped was using a flexible head magnet (see attached photo). That totally saved me when I dropped a couple of bolts down into the abyss... also one of the small metal clips that goes onto the ignition coil. Would have been a major PITA to take off the plastic protector under the car to find it, but instead, all I had to do was go fishing with my flexible head magnet and move it around under the engine and it picked up those bolts and metal clips immediately. Also, having done my 2012 2.5 OB 60K miles ago, when it was at 100K miles, looks like it's time to do it again. After the major PITA that the 2016 OB was, I can't wait to do it on the 2012 again, it was sooooo much easier.Attachments
buying the more expensive dual platinum plugs will give absolutely no improvement over regular iridium plugs. Fuel economy in my 2010 3.6R and my 2014 2.5i was unaffected. engine runs exactly the same.
2010-19
for both the 2.5i and the 3.6R the intake box and battery has to come out. also not a bad idea to lay PS tank aside on 10-14 cars
a 3", universal joint, 12" ext with a ratchet and spark plug socket is all you need
work front to back when removing them
when installing plugs, rotate them counter clockwise until you feel them drop into the threads and then finger tighten. then add universal and 12" and torque to spec.
work back to front when installing them
I have done this job multiple times (3 differnt cars I had and my friend's cars) and imho that is the best way
2010-19
for both the 2.5i and the 3.6R the intake box and battery has to come out. also not a bad idea to lay PS tank aside on 10-14 cars
a 3", universal joint, 12" ext with a ratchet and spark plug socket is all you need
work front to back when removing them
when installing plugs, rotate them counter clockwise until you feel them drop into the threads and then finger tighten. then add universal and 12" and torque to spec.
work back to front when installing them
I have done this job multiple times (3 differnt cars I had and my friend's cars) and imho that is the best way
I took the driver side wheel off so I could get to the 14mm bolts in the frame rail from underneath. I didn't bother putting them back. What a pita.Did my brothers 2016 2.5 with 102K miles a few days ago... he had never had the plugs changed. Yeah, agree totally on the over-engineered 14mm horizontal bolts on the battery tray. I may or may not have only reinstalled 5 of the 6 bolts and not the bottom 14mm one
Changed the plugs and coils on my ‘15 H4 @ 72K miles. The car had some hesitation at around 20mph under light load which seemed to be a coil issue (correct), otherwise I was in no real hurry. It took 5hrs from start to finish working at a slow steady pace, without any hiccups.
I read this thread once or twice before going in and had picked up:
I ended up having a set off wobble extensions from Harbor Freight. Adding one of those to the spark plug socket that already had one worked for pretty much everything. I used the “tight” tool for the hardest plug). The long 14mm wrench was also needed for the battery tray. A set of long needle nose pliers were handy for the coil clips and a telescopic magnet in case something fell down (dropped a battery tray bolt).
I went with the NGK plugs and coils.
IMO, it’s not a nightmare, but you have to have the tools that work/reach properly. Be patient and try not to lose any clip/bolt, just be methodical.
I read this thread once or twice before going in and had picked up:
- 14mm magnetic spark plug socket with a wobble extension (seems pretty standard on Amazon - $10).
- The long 14mm wrench someone else mentioned.
- The “tight” tool that was also mentioned.
- picks (used the 90-degree version).
I ended up having a set off wobble extensions from Harbor Freight. Adding one of those to the spark plug socket that already had one worked for pretty much everything. I used the “tight” tool for the hardest plug). The long 14mm wrench was also needed for the battery tray. A set of long needle nose pliers were handy for the coil clips and a telescopic magnet in case something fell down (dropped a battery tray bolt).
I went with the NGK plugs and coils.
IMO, it’s not a nightmare, but you have to have the tools that work/reach properly. Be patient and try not to lose any clip/bolt, just be methodical.
I went back through, but could find a reference to a "tight" tool. What, exactly, is the "tight" tool?
Thanks.
Post #9
Tite Reach 3/8 Do-it-yourself Tite-reach Extention Wrench Model - Amazon.com
Tite Reach 3/8 Do-it-yourself Tite-reach Extention Wrench Model - Amazon.com
www.amazon.com
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66 Posts
Did this last weekend on my '19 OB. 10 year old son helped, start to finish in an hour. Tools used on the plugs: 3/8 ratchet, craftsman 14mm 12 point deep socket, craftsman 3" 3/8 extension, magnet on a flexible wand.
I used a few other tools for the battery, air cleaner, etc. Biggest win was a serpentine belt tool with a low profile 14mm socket to get the lower battery tray bolts. Only the top one went back on, other in the trash.
I used a few other tools for the battery, air cleaner, etc. Biggest win was a serpentine belt tool with a low profile 14mm socket to get the lower battery tray bolts. Only the top one went back on, other in the trash.
Great that you're involving him while young and teaching him how to do this. And I'll guess that his smaller hands were a help to you in the tighter places!
I hope my spark plug changeout goes as smooth as this last one and I can get it done in an hour.
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66 Posts
Yeah his little hands were a big benefit! I am always trying to get him involved in fixing things so he learns it. We homeschool so it's nice to include many practical things in his education.
GOLDILOCKS '15 Outback Limited 2.5i Tungsten; '10 Outback 2.5i Limited, CVT, Cypress Green 150K miles; '99 Forester S, 247K miles
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378 Posts
I changed my plugs on 2015 Limited 2.5i engine at 118,000+ miles, used the Subaru OEM parts. Really didn't have any issues saying I needed to change, but decided I'd gotten good life from them. Can't say for sure that mpg increased or not, if so, it wasn't significant.
I can't really offer great tips on doing this other than to say that the biggest hassle was getting the battery and tray out of the way because the 2 bolts securing the tray downward were a real pain, and much longer bolts than they need to be, so very tedious.
I did NOT jack up the car or the engine and don't know why that would be needed, based on successfully doing it without that. Here are my notes from this, done a couple years ago, for whatever they are worth.
Odometer 118,134 Installed spark plugs, all 4, and Subaru Air Filter. Rear on each side has slight bit of oil in cylinder. Plugs looked good except front right passenger side was a little more burned and degraded. The rest were actually pretty healthy. All of them were exactly right on gap spec, same as the new ones, 1.1mm or just shy of (.44 hundredths?) I did remove the items recommended on each side for access, the whole air cleaner box on the right, and the whole battery and battery tray frame on the left. Right side was easy. Left (driver's) side was definitely challenging. I absolutely needed the 14mm flex head box end wrench to get out the 2 bolts down on the side of the battery tray frame, but with them, it was not nearly as bad as I was prepared for, from reading reviews and tips. But I only put ONE BOLT back in because the lower one kept cross threading as I tried to reinstall it and I just decided it wasn't worth the fight. It totally does not need two bolts down there, and Subaru installed much longer bolts down on the side than necessary, making the job a lot more hassle than it should be. Getting the plug out from the rear-most cylinder on that driver side was very challenging and I had to switch between several little bit tools to get the plug all the way out. But I did get it all done and all reassembled and I am very glad it's over with for another hundred thousand plus miles!
*The "little bit tools" referenced include universal joint sockets and wobble bits for each size (1/4, 3/8, 1/2) and I may have had to switch between sizes when things got too tight, but I managed to get all of them out and back in fine. I doubt I'd have succeeded w/o removing the battery tray, but someone here earlier said they did, so maybe I should have tried other combinations of tools first? In any case, that battery compartment won't be quite as tough next time with one less overly long bolt to slowly work out and in. (In fact, having the right spec length bolt on hand to go shorter would probably be a good move next time?)
And I know lots of you think you need to change these plugs much sooner than I do, so more power (and hassle) to you. I've always gotten great life and good performance from these quality plugs in both the 2015 and 2010 Outbacks we own, and I'm no fan of doing this job more than needed. Pay attention to mpg and any drivability issues and you should know if they are beginning to get slack on the job.
I can't really offer great tips on doing this other than to say that the biggest hassle was getting the battery and tray out of the way because the 2 bolts securing the tray downward were a real pain, and much longer bolts than they need to be, so very tedious.
I did NOT jack up the car or the engine and don't know why that would be needed, based on successfully doing it without that. Here are my notes from this, done a couple years ago, for whatever they are worth.
Odometer 118,134 Installed spark plugs, all 4, and Subaru Air Filter. Rear on each side has slight bit of oil in cylinder. Plugs looked good except front right passenger side was a little more burned and degraded. The rest were actually pretty healthy. All of them were exactly right on gap spec, same as the new ones, 1.1mm or just shy of (.44 hundredths?) I did remove the items recommended on each side for access, the whole air cleaner box on the right, and the whole battery and battery tray frame on the left. Right side was easy. Left (driver's) side was definitely challenging. I absolutely needed the 14mm flex head box end wrench to get out the 2 bolts down on the side of the battery tray frame, but with them, it was not nearly as bad as I was prepared for, from reading reviews and tips. But I only put ONE BOLT back in because the lower one kept cross threading as I tried to reinstall it and I just decided it wasn't worth the fight. It totally does not need two bolts down there, and Subaru installed much longer bolts down on the side than necessary, making the job a lot more hassle than it should be. Getting the plug out from the rear-most cylinder on that driver side was very challenging and I had to switch between several little bit tools to get the plug all the way out. But I did get it all done and all reassembled and I am very glad it's over with for another hundred thousand plus miles!
*The "little bit tools" referenced include universal joint sockets and wobble bits for each size (1/4, 3/8, 1/2) and I may have had to switch between sizes when things got too tight, but I managed to get all of them out and back in fine. I doubt I'd have succeeded w/o removing the battery tray, but someone here earlier said they did, so maybe I should have tried other combinations of tools first? In any case, that battery compartment won't be quite as tough next time with one less overly long bolt to slowly work out and in. (In fact, having the right spec length bolt on hand to go shorter would probably be a good move next time?)
And I know lots of you think you need to change these plugs much sooner than I do, so more power (and hassle) to you. I've always gotten great life and good performance from these quality plugs in both the 2015 and 2010 Outbacks we own, and I'm no fan of doing this job more than needed. Pay attention to mpg and any drivability issues and you should know if they are beginning to get slack on the job.
1.1mm ~ 0.044 inch = 0.44 tenths = 4.4 hundredths = 44 thousandths
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Ditto on Rock Auto I took pictures Iridium SILZKAR7B11 93482 < got from Amazon but was warned of China nock ruining engines and the latest RutheniumHX LKAR7AHX-S 92274 So I talked emailed to NGK rep in Michigan all where not China nock-offs. China as of last winter hasn't figured out how to make the Ruthehiums per NGK rep.
thanks for posting the plugs bulletin. I have a 17' Forester & Outback (2.5) The pics , torque specs will help
Go to Mr. Subaru YouTube:
The best advice I can give you is to buy the Ko-Kem thin walled Sparkplug socket .
This is the 14mm used for 2.5L. The 6 boxer uses a 16mm socket. Believe me when I say it’s worth the money. I’m old and the job took me 3 hrs - 1 hr on left side….2 hrs for right side. This boxer motor has very tight clearances….and the Right Rear #4 for 2.5L was a royal PITA to get out and harder to install cap. I was fiddling around with the cap and thin wiring until Presto! stumbled upon just the only way to rotate the sparkplug cap & insert boot.
I used both 3/8” and 1/4” ratchets & extensions of several short lengths (1/2” and 1”) along with flex & wobble sockets.
FWIW the sparkplugs looked great at 80k. I used factory OEM and ordered from Rock Auto the specified NGK. And seeing how hard it was….I’m going another 80k for next replacement. By then I’ll be too old to do this 😀!
Some Hints: Dielectric grease & AntiSeize.
1) the Sparkplug boot was almost impossible to pull out - I was afraid that the boot would be damaged. When I reinstalled the Sparkplug boot, I used a Q-tip to apply a very thin coating of Dielectric grease in boot to help next scheduled Sparkplup replacement (@ 160k).
2) Anti-seize on Sparkplug threads - this “Tip” is controversial but I’ve worked on Motorcycles and cars for many years.
I used a very light coat of anti seize by using clean toothbrush to “paint” (very THIN coat) all but last 4 threads closest to Sparkplug firing tip). That makes it easier to thread in carefully with “feel”. I use my 50 yrs experience to tighten by “feel”. You have to carefully tighten….feel wrench bottom …a 1/4th extra turn to seat / compress Sparkplug washer.
Take your time. It’s a hard job but with patience it’s doable. Do not rush! I’ve done this on daughter in law’s 2014 Forester with 2.5L several years ago. It wasn’t that hard … maybe I was younger then? 🤪
I do not recommend this for Inexperienced home mechanics. It also helps to be young - I’ve got some arthritis. Good luck 👍!
Ko-Ken 3300CZ-16 3/8 Sq. Dr. Z-Series 6-Point Clip Type Spark Plug Socket 16mm : Amazon.ca: Clothing, Shoes & Accessories
Ko-Ken 3300CZ-16 3/8 Sq. Dr. Z-Series 6-Point Clip Type Spark Plug Socket 16mm : Amazon.ca: Clothing, Shoes & Accessories
www.amazon.ca
Yes. That 3.6L Sparkplug takes 5/8” or 16mm socket to remove & install.
I believe NGK is OEM rebranded as Subaru plug number. Good luck 🍀!
FWIW if you’re unsure about Sparkplug specs, go to OEM Sparkplug manufacturer (NGK) website and check dimensions under “Shell” for specified Sparkplug.
EG Home - NGK Spark Plugs
I tend to use NAPA or Rock Auto to buy most common Maintenance Parts & check cross references.
Look up part and see “Info” also will give you Sparkplug dimensions (Hex = Socket size)
Pay attention to most popular brand purchased denoted as ❤; but remember sometimes it’s the cheapest part offered vs best quality.
EG I prefer Akebono brake pads & shoes; Wix Oil Filters, etc
If you really want to be sure of correct part (especially for electronics) input your car’s VIN.
I prefer to buy OEM supplier parts if possible from Rock Auto / NAPA. I don’t trust Amazon since you can get counterfeit parts.
I believe NGK is OEM rebranded as Subaru plug number. Good luck 🍀!
FWIW if you’re unsure about Sparkplug specs, go to OEM Sparkplug manufacturer (NGK) website and check dimensions under “Shell” for specified Sparkplug.
EG Home - NGK Spark Plugs
I tend to use NAPA or Rock Auto to buy most common Maintenance Parts & check cross references.
RockAuto | All The Parts Your Car Will Ever Need
Auto Parts for Your Vehicle at Reliably Low Prices. Fast Online Catalog. DIY-Easy. Your Choice of Quality. Full Manufacturer Warranty.
www.rockauto.com
Look up part and see “Info” also will give you Sparkplug dimensions (Hex = Socket size)
Pay attention to most popular brand purchased denoted as ❤; but remember sometimes it’s the cheapest part offered vs best quality.
EG I prefer Akebono brake pads & shoes; Wix Oil Filters, etc
If you really want to be sure of correct part (especially for electronics) input your car’s VIN.
I prefer to buy OEM supplier parts if possible from Rock Auto / NAPA. I don’t trust Amazon since you can get counterfeit parts.
Easy job on a 2017 3.6 Outback. I had hard to remove the coil pack on my wife's 2021 Forester Touring. I take 3.6 all day any day.
2025 Outback. Previous rides: Loyale 5MT, 2005 Impreza 5MT, 2010 Forester 6 MT, 2015 Outback 6 MT
Joined
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1,072 Posts
Good tip on dielectric silicone. I’ve been using it for years, including on all the electrical connectors.Go to Mr. Subaru YouTube:
The best advice I can give you is to buy the Ko-Kem thin walled Sparkplug socket .
![Image]()
This is the 14mm used for 2.5L. The 6 boxer uses a 16mm socket. Believe me when I say it’s worth the money. I’m old and the job took me 3 hrs - 1 hr on left side….2 hrs for right side. This boxer motor has very tight clearances….and the Right Rear #4 for 2.5L was a royal PITA to get out and harder to install cap. I was fiddling around with the cap and thin wiring until Presto! stumbled upon just the only way to rotate the sparkplug cap & insert boot.
I used both 3/8” and 1/4” ratchets & extensions of several short lengths (1/2” and 1”) along with flex & wobble sockets.
FWIW the sparkplugs looked great at 80k. I used factory OEM and ordered from Rock Auto the specified NGK. And seeing how hard it was….I’m going another 80k for next replacement. By then I’ll be too old to do this 😀!
Some Hints: Dielectric grease & AntiSeize.
1) the Sparkplug boot was almost impossible to pull out - I was afraid that the boot would be damaged. When I reinstalled the Sparkplug boot, I used a Q-tip to apply a very thin coating of Dielectric grease in boot to help next scheduled Sparkplup replacement (@ 160k).
2) Anti-seize on Sparkplug threads - this “Tip” is controversial but I’ve worked on Motorcycles and cars for many years.
I used a very light coat of anti seize by using clean toothbrush to “paint” (very THIN coat) all but last 4 threads closest to Sparkplug firing tip). That makes it easier to thread in carefully with “feel”. I use my 50 yrs experience to tighten by “feel”. You have to carefully tighten….feel wrench bottom …a 1/4th extra turn to seat / compress Sparkplug washer.
Take your time. It’s a hard job but with patience it’s doable. Do not rush! I’ve done this on daughter in law’s 2014 Forester with 2.5L several years ago. It wasn’t that hard … maybe I was younger then? 🤪
I do not recommend this for Inexperienced home mechanics. It also helps to be young - I’ve got some arthritis. Good luck 👍!
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