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03-05-2012, 04:54 AM | #1 |
Scooby Newbie
Member#: 311801
Join Date: Feb 2012
Chapter/Region:
NWIC
Location: Portland OR
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Why do 4cyl NA Subarus have 30,000 mile plug change interval?
Just changed the plugs on the EJ22 in my 91 Legacy. The old plugs had a gap of 0.08. No idea how much overdue from original interval.
Manual calls for 30,000 miles and recommends NGK V power, standard core. Ok, that was 21 years ago, fair enough. Out of curiosity, I look at maintenance schedule for 2009 H4 engine. Same interval. My Ford Duratec came from factory with NGK Laser Iridium (Iridium tip with platinum ground backing) and recommended change interval of 100,000 miles, which I think is more typical of today. I'm surprised that Subaru still has 30,000 interval in models today. If Laser Iridium IFR6E11 were used in the EJ22, could you expect 100,000 mle life from them?
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03-05-2012, 12:55 PM | #2 |
Scooby Specialist
Member#: 118500
Join Date: Jun 2006
Chapter/Region:
MWSOC
Location: Michigan
Vehicle:02 Silver Wagon "Stage 2" |
Yes, you could expect around 100k miles. Depends on driving conditions.
OEM's use standard nickel v-power plugs b/c they are cheap, and they don't have a goal of 100k mile replacement interval. All Ford vehicles (post 2007 at least) have a 100k mile goal for spark plug replacement, hence the use of iridium. |
03-05-2012, 02:39 PM | #3 | |
Scooby Newbie
Member#: 311801
Join Date: Feb 2012
Chapter/Region:
NWIC
Location: Portland OR
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Quote:
I believe Toyotas used platinum even in the 90s especially in their V6 cars with plugs that are hard to reach. The plugs on Ford Duratec engine is very easy to change. Full access from the top. The EJ22 in Subaru is more difficult. So, 100,000 mile interval makes sense. |
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03-05-2012, 08:00 PM | #4 |
Scooby Guru
Member#: 137398
Join Date: Jan 2007
Chapter/Region:
E. Canada
Location: Toronto
Vehicle:2004 Impreza |
Long story short: Use the plugs you want to use. Change them as often as you like.
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03-05-2012, 09:27 PM | #5 |
Scooby Newbie
Member#: 3409
Join Date: Jan 2001
Chapter/Region:
NWIC
Location: Oly
Vehicle:98 My FMIC Is bigger than yours. |
DOHC Subarus have platinum or iridium plugs.
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03-06-2012, 08:42 AM | #6 | |
Scooby Specialist
Member#: 118500
Join Date: Jun 2006
Chapter/Region:
MWSOC
Location: Michigan
Vehicle:02 Silver Wagon "Stage 2" |
Quote:
But, in my experience, price is the biggest factor. An OEM can buy an iridium plug for around 2 dollars apiece, but a nickel plug for maybe $0.75 per piece. That's 1.25 a plug or $5 per vehicle if it's a 4 cylinder. Mulitply that over the hundreds of thousands of vehicles produced, and you get an idea of how big the savings is. |
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