Subaru: waste spark wear pattern on cyl 1 and 4

[LoneRanger]

2009 Forester, 41,925 miles (67,471 km).

So this is why Subaru specs 30,000 mile spark plug replacement interval on the non-turbo EJ253 engine which uses a waste spark ignition. Note the extra wear on the platinum center electrode for cyl's 4 and 1 compared to 2 and 3. These are the factory original NGK FR5AP-11 double platinum plugs which I changed out today.


4 - 1 left to right:

1 - 4 left to right:

All in all they're not terrible bad but I'm glad I didn't leave them a lot longer.

 

[NHGUY]

Double platinum but I see no platinum pad on the ground electrode.Maybe they fell off...

 

[WobblyElvis]

I'm confused. First I'm not sure I see much of a difference.

If plugs 1 and 4 use the same coil and fire at the same time, wouldn't there be wear on the centre electrodes of one plug and wear on the side electrode on it's mate?

I have a 2.2 ecotec engine that uses a waste spark. Plugs are original with 146,000 miles. They are iridium and still work fine.

Edit...wait a second, I get it, it's one of them boxer engines..

 

[ARB1977]

My Tacoma has the same system. They use double ground platinum plugs with 30K intervals. I've gone 60K on iridium plugs with no issues.

 

[JTK]

Not all EJ253's recommend a 30K mile park plug change. The "PZEV" version in my 2012 Legacy stated 100Kmi.

 

[splinter]

Should be considered somewhat normal and typical with a 'waste' spark system's reverse polarity.

Curious that the so-called ground straps also seem to have experienced comparatively greater erosion as well.
Perhaps it's merely an optical illusion?

^ photo credit unknown fellow BITOG member.

 

[HerrStig]

Some waste spark systems have a coil pack for every cylinder. No polarity difference. How many coil packs on a three or a five?

 

[sxg6]

Was there oil in your spark plug tubes when you pulled the wires out? Looks like the spark plug tube gaskets are leaking. They're a pain to replace, but subaru redesigned the gaskets so they seal better and shouldn't need to replaced again.

 

[MrQuackers]

I read that an employee of NGK does periodic rotations to maximize the lifespan with this system. Still these look OK for all those miles.