tell them you are going to interview for an internship in the summer but you have to drive there since you need a car to get around that city
Your 18 with your own vehicle why an excuse? You have a friend in need, maybe sick family member, orientation for a job, have to do a couple days in county, I m curious why you need an excuse?
Tell the truth, you need to get away for a few days to get laid.......if that dosnt work try the old looking at colleges or Womens retreat xcuses.
You are doing a sponsored sleep and must not be disturbed.