Is the OEM filter socket made of plastic?
No, it's steel.
I was using the STP filter from Autozone at about $6.... but they stopped selling them so I went with the OEM Suzuki filter.
However, Autozone (and most auto parts stores) sell the same style wrench filter-caps in various sizes. I found one that fit the STP filter for about $4 as well back when I was using the STP filter.