The 2 AM spark plug reading that changed my compression test process

Last Tuesday I was up in Lubbock swapping jugs on a Cessna 172 and the owner kept asking why I bothered checking the plugs before I pulled the cylinders. He said he'd had three mechanics before me just yank them and go. I told him I was looking for lead fouling patterns, and he laughed, said that was some old A&P superstition. But after I pulled #3 and showed him the electrode was melted sideways, not just dirty, he shut up. That one visual told me more about the valve timing than any borescope could. Now I spend 5 extra minutes on every compression check reading the burn, and it's caught two exhaust valves going soft that the cold test missed. Anyone else still trusting spark plug visual clues over the gauges these days?

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