They didn't used to be, of course. From the spur's opening up until around the time of the pandemic, there was something like one or two services a day either worked by a pair of 165s or a 172. Then there was the daily 68 of course. And pretty much everything else for the whole day was solid half-hourly 168s.
I noticed they'd changed to almost all 165s recently and created this thread to enquire about it:
Why did Chiltern's Oxfords go from being a 99% 168 operation (there was I think one daily 165/172 but aside from that it was very rare) to being almost exclusively operated by pairs of 165s? This seems like quite a major downgrade, and strange seeing as so many more 168s seem to be popping up on...
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