Hey y'all. Changed the spark bangers in my gf's '06 Subaroo outback and I noticed something weird. I just bought her the car and therefore don't know the service history. I have attached a picture of the plugs, they're in numerical order from left to right. In the attachment you'll see that the spark plugs on the outside(cylinders 1&4) the electrode is worn down the the insulator where as the two on the inside are looking pretty decent and may still have about 15k of service life left. I've known lazy jiffy lube techs that would skip out on changing hard-to-reach spark plugs if they were in a hurry, but the cylinder 1 plug(left) is by far the easiest to change. The car has leaky valve cover tube seals and cylinders 1 & 4(the ones with the more worn out plugs) had more oil in them than cylinders 2&3. Would oil cause a higher resistance in the ignition circuit leading to shortened plug life? I just thought that I'd throw this out to you all here as food for thought. I know it has been interestimg for me, so perhaps the mechanically inclined and curious amogst you will aswell. It has all new ngk iridium plugs now and I'll have that tube seal problem fixed before long.
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