I changed the spark plugs in the '87 325iC last night. I've only had it for a couple of months so I don't know the last time they were changed. I've heard you can learn a lot by reading the plugs. Besides the fact that my valve cover seal isn't so hot and it's leaking oil down onto the plugs from the outside, what can you learn from looking at these? Sequence is back to front of engine from left to right in the picture. I think #6 has more build-up than the rest. Is that significant? What else can you see?
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