Headers & 90 degree oil filter

Only a small percentage of the oil passes
through the filter at any one time.
Although it would be nice if no heat was
transferred to the oil through the filter,
it is only a small amount and not detrimental
to the oil or the ability of the cooling system to
transfer the heat away.

If it is a concern, you could run a remote filtering system
that is away from that heat source and might possibly
do a better job of filtering the oil.