The abs sensor hole must have something in it to stop the oil coming out. Running without wouldn't be much different to leaving the filler plug off. I'm sure a second-hand one could be picked up cheap enough though. If your not using the abs then it doesn't matter if the wirings shagged on a used one. If it has been run like this then maybe the oil just spread to other parts on the outside of the FD? Maybe the big seal is ok after all? FD's only hold about 250ml, but even a small amount will make a big mess. GL5 is just the spec, GL4 is not good enough (although I cant substantiate this, its just the spec given by bmw), Halfords will do it cheap enough.
Edit: Dr F gives the reason for GL5 above.
Edit: Dr F gives the reason for GL5 above.
