It will hit 5% before it hits 0% then it starts indicating the number of miles past due. It's not like the oil instantly fails the moment the MM indicates 0% remaining. Think of the expiration date on a carton of milk - it's usually good for days to a week or more past that date. My OCD requires me to change the oil (and that gallon of milk) the moment the MM hits 15% and the first notifications appear, but my knowledges knows this is a bit of a waste. Enjoy your trip and don't worry about your oil. Make sure the oil level is okay and you'll be fine.