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Discussion Starter #1
I don't want to start a thread on "how to", this is about spark plug selection.
I have spent the last two days looking for the correct plug to use and everywhere I go, there are different suggestions. I have an 06 ob xt and the manual states, the "recomended plug" is the NGK ILFR6B. When I search for that plug at different vendors, it comes back not compatible. On the LGT and NASIOC forums they suggest different plugs. I am looking for the stock replacement, not one step colder. Before I order the wrong plugs I am looking for some info. Are the NGK silfr6a the correct plugs? Whe does the manual suggest different? Will the correct plugs come with the proper gap?
 

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It boils down to and NGK iridium with a heat range 6. NGK 6481 at your local parts store. Denso equivalent is SK20HR11 or 3421. Either one the plug to use.
 

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Onyx, 2008 LL Bean 3.0R and 2017 Honda Civic Hatchback Sport Touring
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Hold on there partner. Modern plugs come pre-gapped. Many folks think it can't hurt to double check with a gauge. The problem is that using a gauge to gap the plugs can scrape of the coating, like iridium, from the contacts, degrading the plug's performance at running temps.

I've always used NGK for my Japanese cars. IMHO stay away from Bosch.
 

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according to the globaldenso site, that Denso plug is pre-gapped at 0.044 (1.1mm, thus -11)


DENSO SPARK PLUGS



the NGK NGK SILFR6B is pre-gapped at .032 I think (0.8mm)

also, the NGK 6481 is not listed for his car(though, it may work fine - I dunno) at the NGK parts finder. The Iridiums which are listed, both show a gap of 0.30"; http://ngksparkplugs.com/part_finder/car_truck_suv/results.asp
 

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Hold on there partner. Modern plugs come pre-gapped. Many folks think it can't hurt to double check with a gauge. The problem is that using a gauge to gap the plugs can scrape of the coating, like iridium, from the contacts, degrading the plug's performance at running temps.

I've always used NGK for my Japanese cars. IMHO stay away from Bosch.
co-worker just had a bad experience with Bosch in his daughter's Camry, I told him to get NGK and now it's running fine.

I think I'd avoid Bosch, too many anecdotal failures to risk it.
 

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I don't want to start a thread on "how to", this is about spark plug selection.
I have spent the last two days looking for the correct plug to use and everywhere I go, there are different suggestions. I have an 06 ob xt and the manual states, the "recomended plug" is the NGK ILFR6B. When I search for that plug at different vendors, it comes back not compatible. On the LGT and NASIOC forums they suggest different plugs. I am looking for the stock car accessories replacement, not one step colder. Before I order the wrong plugs I am looking for some info. Are the NGK silfr6a the correct plugs? Whe does the manual suggest different? Will the correct plugs come with the proper gap?
I am not completely sure but you need to try eBay site to get right plug..
 

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Discussion Starter #10
See, with just these few posts, confusion. SILRF6B is not the same as SILRF6A? FCP import and another site recommend SILRF6A. I want the OEM plugs. Car did not come with denso or Bosch but NGK (Japanese). I am just wondering on why the different NGK numbers especially from what the maintenance Manuel recommends?
 

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See post 3 above. The SILR6B rolls over to the 4 digit number the parts stores use.

I don't use Bosch plugs either. Too many oddball failures.
 

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2008 subaru outback 2.5i
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Why not take out the spark plug and see whats in the car and get replacements with the same part number on the current plug, thats what i would do
 

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Why not take out the spark plug and see whats in the car and get replacements with the same part number on the current plug, thats what i would do
it 'seems' likely that the original part or number is being replaced with a different 'service replacement' number. At least from what I saw at the NGK site. But, a dealer may be working from older stock or perhaps the OEM number is 'reserved' for dealers?

anyway, it isn't just a little confusing here, seems that legacygt and other forums exhibit conversations in which folks are confused. Add to that whether or not a plug arrives properly gapped - and it can be frustrating. (personally, I wouldn't trust that a bosch or denso cross-referenced plug was gapped correctly)

there may very well be half a dozen or more NGK parts that will work, but what will actually work best and last longest is another issue. Flat4 said he wants what came in his car. That may require finding a dealer with the older part number or buying the ones I saw on ebay in Subaru boxes.
 

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I don't get it.

Did anyone look at the NGK reference sheet on their website? It breaks down the part numbers and what each section of the number means. It can't get any easier than that other than I provided the interchange number the parts stores use. Its the same part.
 

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the a and b suffixes mean 'special' , but may not mean 'identical' according to; http://ngksparkplugs.com/docs/tech/design_symbols_plugs.pdf

and the denso part you listed is gapped too large. (but so is the Iridium IX part shown on NGK's part finder ???)


NGK Spark Plugs USA

shows;

Cars, Trucks & SUVs

2006 SUBARU OUTBACK XT 2.5 H4 EJ255 FI Turbo
Spark Plug Part No. Stock No. Plug Gap

OE Laser Iridium SILFR6A ^ # 7913 .030

Iridium IX LFR6AIX-11 6619 .030


# Original Equipment Manufacturer, and/or Original Equipment Service Part
^ “Laser Series” Iridium center electrode, and Platinum pad ground electrode

ILFR6A is part #3588, flat4 could do a shopping search for it. They sell them on ebay and Amazon.


I have no idea why the part finder page at NGK would disagree with either cardoc or other NGK publicATIONS. I CERTAINLY am in no position to challenge either source.
 

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The spark plug gap is predetermined according to the electrode type and heat range. Differing electrodes set off different temp/strength sparks and the gap is imperative to proper ignition. So the preset gap is not an issue unless it is altered prior to installation. The issue is the type, size and heat range.
 

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Discussion Starter #18
So I drove the 60 miles to the dealer yesterday to get the low down. After reading through enough posts and discussions only to discover no one knows for sure why the maintance manual suggests different from everywhere else, I had to go to the source. I tried calling the parts guy but he was no help, so I went to visit my Subaru master tech guru. He said that the ILfr6b has no Platnium on the tip where the the SILFR6A has the Platnium. Both plugs will work, one is a little better! That being said, yes the car had the latter plugs installed but I was not sure on the service history of the car. Just bought it with 106,000 miles so wanted to be sure. Also, the SILFR6A is not available anywhere local to me besides dealer $19.00 each. My issue was compounded by the fact that I had already pulled the plugs out so I did not want to wait the few day for shipping plugs.
 
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