Jesus is the bridegroom, the oil is the Holy Spirit, which lights up the eye of our heart so that we can see Jesus whenever he appears. The foolish virgins wasted their oil, they did not replenish it through the sacraments of prayer, coupled with works of charity and mercy.
We cannot see Jesus without the oil of the Spirit. When he comes into our life, if we have not nurtured ourselves in such a way that our lives are in tune with Christ and the Spirit then Jesus shall catch us unawares.
These parables of the last few days are constant warnings that the Kingdom of Heaven must be looked for and the attitude of seeking Jesus must be nourished in the prayers and sacraments of the Church. So fill your lamp with oil!