The miracle of Chanukah that we commemorate was that the oil burned for 8 days, until they were able to replenish it. Why did it take 8 days to make new oil for the menorah? The normal process for making oil doesn't take that long. Furthermore the talmud (peah) discusses olive trees who's produce is so full that oil literally leaks out. Couldn't they have accessed usable oil more quickly?
There are two explanations provided for the eight day delay in getting new ritually pure oil.
One opinion is that the oil was produced in a region that was a four day journey from Jerusalem. This is the explanation of the Ran on Shabbos 21b. The Meiri identifies the oil producing region as Tekoa.
The other opinion is that the delay was because they were all in a state of tumas meis - ritual impurity resulting from contact with a dead body, and it takes seven days to be prufied from such tumah. Only after they were tahor - ritually pure - would they be able to produce ritually pure oil. (See Beis Yosef OC 670)