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Old 01-27-2013, 10:16 AM   #1
Sid03SVT
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Question spark plug ?'s 08 2.5i Leggy

Alright I went through the spark plug FAQ and couldn't find my answer there, yes I also used the seach button.

So I'm going to perform a plug swap on my mother-in-laws 08 N/A Legacy; same engine as the 2.5l impreza so heres my question.

The Manual lists 30k intervals for plug changes, are there any plugs that will last say 60k miles instead?

It's not that I'm cheap (well a little) or lazy (well a little) the plugs are just kinda a P.I.T.A. to do in these flat engines and 30k feels way to frequent for me; not to mention that every 60k I'll be doing mine too.

funny story, my wifes Toyota, I don't have to touch anything except for oil/filter and air filters until 100k. I went through her maintenance log and cried a little thinking about mine, but then I remembered it was a Toyota and that my soul dies a little bit every time I drive it. New toyotas also have 10k/1yr OCI's, still not enough to make me want to get one though.

Anyways,

AtDhVaAnNkCsE
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Old 01-27-2013, 11:23 AM   #2
Elbert Bass
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Legacy 2.5 NA plug interval was 30k up to 2009 and used a shared 1 coil per two cylinders in a waste-spark configuration. 2010 switched to 60k interval but also switched to coil-on-plug with a coil for each spark plug.

Those are two VERY different ignition schemes and the way in which they work dictates the service interval. Your 2008 waste-spark system requires plugs every 30k because the plugs actually fire twice as many times as in a coil-on-plug system. I wouldn't try to "upgrade" and "extend" the service interval - you won't be doing the engine or your catalytic converters any favors trying to make your life easier.

I won't address the Toyota service interval - in this discussion that is comparing apples to oranges (even though they come from the same "farmer").

Last edited by Elbert Bass; 01-27-2013 at 11:34 AM.
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Old 01-27-2013, 12:53 PM   #3
cal_look_zero
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The plugs are only $33 or so at parts store, and took me 25 minutes my first time. Just pull the battery and the intake tube, and have different sized extensions available. The 08 I did had similar plug entries to my 97; not like the damn DOHC/WRX ones right in the middle of the head.
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Old 01-27-2013, 01:21 PM   #4
Sid03SVT
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Quote:
Originally Posted by Elbert Bass View Post
Legacy 2.5 NA plug interval was 30k up to 2009 and used a shared 1 coil per two cylinders in a waste-spark configuration. 2010 switched to 60k interval but also switched to coil-on-plug with a coil for each spark plug.

Those are two VERY different ignition schemes and the way in which they work dictates the service interval. Your 2008 waste-spark system requires plugs every 30k because the plugs actually fire twice as many times as in a coil-on-plug system. I wouldn't try to "upgrade" and "extend" the service interval - you won't be doing the engine or your catalytic converters any favors trying to make your life easier.

I won't address the Toyota service interval - in this discussion that is comparing apples to oranges (even though they come from the same "farmer").
Thanks for that - I was not aware that was how the ignition system worked, now I can see why they chew through plugs in 30k miles.

As for the Toyota intervals, I was just suprised how long that car goes before you touch anything aside from the above mentioned items; yes Toyotas and Subarus are very different cars.
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Old 01-28-2013, 12:48 PM   #5
08 OutbackSport
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Lol don't forget about the differentials. Subaru calls for those every 15k miles
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Old 01-30-2013, 07:23 AM   #6
Elbert Bass
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Quote:
Originally Posted by 08 OutbackSport View Post
Lol don't forget about the differentials. Subaru calls for those every 15k miles
Not sure where you get your information from, but the Subaru maintenance schedule in the FSM begs to differs.

Subaru normal maintenance schedule from the FSM states Inspection every 30,000 miles for 2008 models - no service interval. The ONLY condition you are required to change the ATF/MT gear oil and differentials is when used for repeated duty towing.

At our shop we recommend every 45,000 to 50,000 mile service interval. We are in the Appalachian foothills so we see moderate mountain driving. That seems to work best for the vehicles and our customer's budgets since it is between major maintenance intervals.
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Old 01-30-2013, 10:30 AM   #7
Eyedoc Orlando
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On my 2007 with a waste spark type system, I had great success going 60K Miles on Bosch Fusion IR Plugs. They worked so well I went for another set at 100K.

I use nothing but Amsoil Severe Gear in the manual transmission, and it's good for 60K as well. However I change the rear axle fluid every 30K since it holds less than 1 qt and is simple to do. I'd rather have clean fluid back there
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