I would just say, "Hey sorry I worried you but it was a last minute thing, or I didn't want to drive home late, or I didn't want to call and wake you up." Make it that you were thinking about them. If they get hard, you can say, "You're right, I should have called you." When parents are trying to manipulate, just repeat that they are right. That's what they want to hear. And in reality, you are 18 and you have enough sense to know right from wrong. You are absolutely right that you have the right to stay out all night without telling anyone if you want, because the reality is, you are going to be away at college. However, you have to blow smoke up their *** because they pay your tuition.