Broadly speaking, the 165s will work local services as far as Banbury plus the Leamington Spa - Birmingham/Stratford-upon-Avon shuttles, 168s will primarily do Birmingham and Oxford services and the 172s will also do Oxfords, just as they all do during the rest of the week.
172 diagrams used to appear in the "Frequently Requested Diagrams" post, given Chiltern only have four of them, but were taken out a couple of timetable changes ago.