Jump to content
Ultimate Subaru Message Board

What type of plugs does subaru use?


Recommended Posts

Some models do, indeed, come with Champions (in fact the early 2.5RSs (including my '99 model) came with Champion Platinums standard), but NGK is pretty much the standard plug. Also, every Subaru dealership I've seen uses only NGK for replacement plugs regardless of what they came with originally.

 

(Don't quote me on this but I had heard in the past that using Champion plugs was part of Subarus way of getting around some kind of certain% made in the USA type rule/law (as NGKs are made in Japan and Champions are made in the USA).)

Link to comment
Share on other sites

I will copy over some info from previous posts I have made on the subject.

 

I used PFR5B-11 NGK which I found at advanced auto for $10, best price I found, and yes those are the original equipment plugs for the car. List on those plugs most places is $15 each and a lot of the internet sources wanted $12 or more with shipping extra. My kid who is on a budget bought Autolite APP3924 for about $4 apiece. They are double platinum and made in America. Very high quality appearance and seemed to match the NGK's for dimensions very well. The car runs like it should on them, so they may be OK to use. The plugs on this engine are real difficult to change, so I bought the NGK not wanting to have to redo the job if there were any problems

 

Once you remove the windshield washer bottle and battery (can probably just slide it forward on it’s tray a bit) on the left and the air inlet tube and mass air sensor and air cleaner box on the passenger side, access is fair doing a 2.5 in an outback. I would do the front plug first on each side, as they are slightly easier to do. What makes it the most hard is that the plugs are really far down inside the wells in the heads. The rear plugs on each side are harder because the frame rails are closer in the back. My problem was that an extension was needed, but there isn’t room to get one in with the socket attached. You have to slide the socket into the hole first, then slide in and assemble the extension, and finally attach the ratchet to the end of the extension. I immediately removed the sponge rubber plug protector from my socket, the reason being it will be extremely difficult to get the socket off the end of the plug and out of the hole if the rubber is gripping the spark plug. I didn’t want it on for plug removal either, because there is a lot of trial and error with your socket set as to what gives just the right length for getting the socket stack down into the hole. As I recall, what worked best for me was to use a plug socket in the rear, and then use a ratchet with a standard socket on it to turn the hex on top of the plug socket instead of using an extension. On the front plugs, a 3" extension worked pretty well with the regular spark plug socket and a ratchet. There was at least one plug which worked slightly better with a standard deepwell socket instead of the spark plug socket, but that was not a critical must have item! I would recommend having a small hand mirror on a stick or a ladies compact to be able to glance down into the well to see what’s happening. I’ve done a few of these cars, and on each one, at one time or another, the spark plug socket became slightly jammed on some aluminum protrusions of the head that were down deep in the well. The impression is that the threads are pulling rather than the socket is cocked and dragging. If you experience this, Use the mirror to reconnoiter. If in doubt, reverse direction, and the condition should go away if it’s not the threads. This usually happens when it’s just starting to go real good to scare the heck out of you.

Going back in with new spark plugs, make sure you check the gap first, then lube the threads with an anti-seize compound. Make sure there is a washer on the plug or you will wonder later on if it was in fact there. The big trick for installation, is to have a piece of rubber hose that’s about three or four inches long and a snug fit on the top of the spark plug. Stick it down over the top of the plug and use it to guide the plug into place. Twirl the hose between your fingers and you can probably get the new plug in half to three quarters of the way which ensures the threads are started straight. It's also much quicker and easier than a socket wrench as far as it will go. Putting all the stuff back on after the plugs are in, make sure the three quarter inch hose that connects to the bottom of the intake tract after the air flow sensor is reconnected, The car will not run without the hose connected, and sometimes it slips off unseen during disassembly, and you don’t even realize it needs reconnected.

Link to comment
Share on other sites

I believe the phaseII 2.5's came with Champion copper plugs from the factory, at least my '02 OBW did. (Replaced with plat. NGK's).

 

Let me know if you need the part numbers, I probably still have the old boxes around.

you really should replace those with copper NGK's

Link to comment
Share on other sites

Not a big fan of the platinums for these motors Thawa?

 

I didn't realize ngk had double platinums.. I'm using the cheap ($2.50) regular one's (G-power) and they've been fine so far, maybe in 15k i'll throw in some of the v-groove's.

Link to comment
Share on other sites

  • 2 weeks later...
Not a big fan of the platinums for these motors Thawa?

 

I didn't realize ngk had double platinums.. I'm using the cheap ($2.50) regular one's (G-power) and they've been fine so far, maybe in 15k i'll throw in some of the v-groove's.

That's not it at all. platinum is a less conductive metal than pretty much anything else. They're only good for longevity. Copper is much more conductive than platinum or iridium.

Link to comment
Share on other sites

That's not it at all. platinum is a less conductive metal than pretty much anything else. They're only good for longevity. Copper is much more conductive than platinum or iridium.

Platinum lasts longer, with less erosion. The difference in conductivity is negligible, especially when you consider the resistance of the wires.

Link to comment
Share on other sites

It's important to use double platinum rather than single platinum for correct operation. The reason is with our ignition system, half the plugs the spark jumps center electrode to side electrode, and the other half the spark jumps side electrode to center electrode. There was a very long discussion on how and why this is in the past. Regular plugs will wear differently between the two sets over time, and this will affect operation.

Link to comment
Share on other sites

As far as I know all modern plugs use a copper core (even the platinums and iridiums). It's not done for reasons of electrical conductivity, but for thermal stability (it widens the effective heat range).

 

Also look closely at the manufacturer specs for the fine-tipped iridiums and you'll notice that they are rated for 30K mile service life, not 100K as is commonly stated. Special, wide-electrode (normally sized) iridium plugs are available that are rated for a service life of 100K.

 

The only advantages of using a fine-electrode plug is an easier ionization path (like a lightening rod), and less mixture shrouding. This can benefit emissions engines that are experiencing a slight lean-misfire condition (throttle tip-in stumble), or forced aspiration engines that require a closer plug gap to prevent misfire under boost.

Link to comment
Share on other sites

New Subaru owner. I just got a '95 Legacy. 150,000 miles--looked like the plugs had been in there a loooong time. I replaced them with Bosche plugs--didn't notice anything "bad" about them yet.

 

 

 

Has anyone run Splitfire plugs in your Subaru? I was curious about them. I loved them in my Chevy smallblock a few years back...wasn't sure if they did anything for Subarus.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...