Depends on the vehicle. Some require a regular box end or combination wrench. Some are designed so that a ratchet plugs directly into it.
13mm
15mm.
14mm
The 2006 VW Jetta oil drain plug will be on the bottom of the oil pan. You can remove the drain plug with a 9/16 wrench.
It is a metric bolt and I believe it's a 15 millimeter.
17 mm.
The original engine oil drain plug wrench size should be 15mm.
If the drain plug is original equipment, it takes a 17mm wrench or socket.
If it's the "oil" drain plug, the size wrench is, better yet use a socket wrench=13mm.
15mm
It seems to me I use a 15 mm wrench to remove the engine oil drain plug.
You didn't say what year you have but it should be 15mm.