Us modern Volvo guys have the same problem. The plug holes are just too damn deep. Usually, any oil spilled from the filler cap, whether from adding oil or an old cap gasket, will drain into one of the plug sockets.

Sop out the oil with cloth or paper towels. When it is almost dry, pull out the plugs. You will want to replace the plug wires, all of them, and probably the plugs as well, just because they are out.

Klaus
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The 164 has a new home, all I am left with are a 95 854T and a 98 V70R :)

Are you talking about spark plugs being inside tubes running through the valve cover?

If so, either the valve cover gasket is leaking, the tubes are loose, or someone's hands were shaking when adding oil.

I'd start by sopping up the oil with paper towels and then replacing the valve cover gasket and whatever seals are associated with the tubes. On my Camry the tubes have no seals on the bottom, they just thread into the block. I've been told that coating the threads with some sealant fixes that.