After almost 100k miles, I just replaced the plugs in my mother's old 01 Forester, for the first time. Put in some new NGK's in with a 0.035" gap. Old plugs looked ok, a little white but the gaps measured at least 0.075"!!!

 

Wondering if it was caused by wear or if the orginals really had a huge gap?

 

Also wonder if my "hard to start" conditions could have been related to these plugs?

 

Any comments? (That is other than "it's a good thing your mother drove a Subaru that could take really take abuse".)

it was definitely the first time they were ever replaced, were they NGK's? wondering if someone previously installed some non-NGK stuff.

 

were they all even, about the same? i'm guessing fairly close. i'm not too surprised of that gap after 100k, so i wouldn't worry about it too much if they're all similar.

They were Champion plugs; I thought that’s what Suabru’s came with.

 

The gaps were within a 3 mil tolerance (can you tell I’m an engineer). The side electrode looked good with fairly sharp corners, but the tip if the center electrode was very rounded and barely sticking out of the insulator.

 

I just read on the NGK website “how do I read a spark plug” normal wear in a four stroke is 0.00063~0.000126 inches/1,000 miles, so for 100,000 that would be 63 to 13 mils. I suspect I got 30 to 40 mils of wear, depending on what they started at.

they were replaced before, so the wear you mentioned doesn't mean much.

Subaru's all come with NGK plugs and for these engines it's a very good idea to stick with NGK's.

Hmm. Maybe a dealership replaced them. I don’t know of a way to tell. I guess it doesn’t make a difference, now it’s got the good NGK plugs in and is gapped properly.

 

Though I did read about Champion plugs being OEM:

 

“…it's not uncommon to find that your Subaru came from the factory with Champion plugs” Peaty 01-16-2007, 04:37 PM

Link: http://www.scoobymods.com/forums/archive/index.php/t-3017.html

 

Also,

 

“Many Subarus come with Champion Plugs (US parts content) and they are notorius for causing mis-fire codes.” SubyTechMaster 11-10-2001, 05:57 PM

Link: http://forums.nasioc.com/forums/archive/index.php/t-111576.html

My new 2002 Forester came with Champion RC10YC4 plugs from the factory.

well there you go, like you said, either way you've chosen a better path by going with the NGK's. they come widely recommended for EJ series engines and cause the fewest issues.

My new 2002 Forester came with Champion RC10YC4 plugs from the factory.

 

That's the exact model plug in the 2001 Forester! Still got them since I wanted to closely look at the yellowing of the insulator.

lots of Subaru's come fron the factory with Champion plugs. there are certain year/model combinations that came with NGK.

~Erik~