8mm hex socket stuck

[911monty]

Jay Sorry but I disagree. Don't put any tools on that flange yet as that is the sealing surface. Any bite marks or distortion of that surface can result in leaks or breakage.
The next thing I'd do is put the hex socket together, then using an 6" ratchet extention while loosening gently rock the extension back and forth.

Edit: I'm also assuming this is Ciao's first oil change, as this is really a common occurrence using a hardened bit in that soft aluminum.