Trying to remove the cover under the fuel filter on my 91 300ce.  Got
all of them off except for one which will not budge.  I'm using a 10mm
socket which is the right size (9 is too small) but the socket just
slips when I turn it counterclockwise.  I cleaned the grease off but
it's still slipping.  I REALLY do not want to take a drill down there,
and the space is too tight to get a vise grip in there.  Any ideas?