we are hanging two wood doors in an outdoor archway.
The doors are now bare wood and the arch will provide
very little weather protection to the doors facing
east and west (at latitude ~41 degrees).

We seek a simple environmentally sound protective coat
for the doors.

Is linseed oil a practical choice?
or Tung oil?
or ?????

A natural oil which doesn’t result in a cracked and peeling
finish a few years from now is preferable.

Any suggestions???