Lycoming oil filter

[Nick Allen]

This may answer the lead content question: http://en.wikipedia.org/wiki/Avgas

[Alan George]

I can now confirm it is a B & C adapter.

We have not had much oil spillage when changing the filter as that Champion filter has a non-return valve so the casing remains full of oil.

[Julian Bone]

aero engines have considerably more blow-by than modern car engines so combustion products acid etc probably reach the oil to a greater extent requiring more frequent changes.
personally I prefer S100 if the machine is often unused for several weeks
filter screens have worked well for many years I have not heard of a good reason to change
the main priority is for the engine to keep going nothing else matters much