“When the Chashmonaim lit the oil, it did not burn for eight days straight. Sorry to destroy your childhood. “
As iBump pointed out, there are at least 100 answers for that famous question of the Beit Yosef. One of those answers, which the B”Y mentions, was that the oil lasted 8 days. The other two were 1) the 1/8 per night that lasted the whole night 2) After pouring the oil out of jug into the menorah, the jug still remained full.
See this thread: http://www.theyeshivaworld.com/coffeeroom/topic/kasha-of-beis-yosef