The Chasam Sofer explains that they had to light outside in the chatzar, in the yard because everything was tamei, so it used more oil. The Maharsha in Chulin (54,2) explains that in order the menorah should not become tamai they took a big earthenware container (kli cheres) and broke it into small pieces that holds less than a half a lug, so teves nights when the night is longer, was not enough even for one day.
Reb Moshe says to remember the first day the fact that oil burns is also a neis. The Chasan Sofer says that the Yevonim went into the Beis Hamikdash and were not metamei from outside having the Beis Hamikdash become chulin (uvou bo peritzim vechuleliho) was a neis. The Pri Chadash that we commemorate the victory the first day.