No, the porcelain really needs to get cleaned. And grit blasting is the only way. I sometimes wire brushed deposits from plugs during the leaded gas/12,000 mi tuneup days, but I don't think that's a good idea anymore.

I'm fortunate that I've always had a grit blaster at my disposal.

I've seen a tool made specifically for cleaning spark plugs. All you need is shop air. It's basically a hand held grit blast gun with a bag that recycles the abrasive. J C Whitney may have it.

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95 E320 Cabriolet, 169K