You can change just the oil but what frequency do you normally change it? Harley recommends changing every 5000 miles. A lot of people change it at 3000, some 2500 and many variations. If you have less than 5000 and your trip isn't going to be very many miles I wouldn't even bother. A few extra miles on it will not make a big difference. But if you can get your hands on a new filter it doesn't take much more time to go ahead and change it too along with the oil. I use synthetic oil. One advantage is the fact that it will not loose it's lubricating properties in such a short period of use. It may keep it's lubricating abilities for 10,000 and much much more. It's not that it doesn't need to be changed as often though because the acids and contaminates that build up can hurt the engine parts if left too long. But a quick trip in time, even though lots of miles, doesn't give the acids/ contaminates from combustion time to work on the engine parts to do the harm that they would over an extended period of time. So going over on the recommended milage is not so bad if it's changed right away after the trip. This is my opinion and this subject is very controversial so opinions will vary. I change my oil every three thousand miles most of the time.