I just purchased a 2005 Suzuki Boulevard C50 and am planning on winterizing it. The previous owner always used Repsol synthetic in the bike. I have been looking at what to do to winterize the bike and most say to drain the oil and refill with new before storage. Then empty again before driving in the spring. Is this necessary with synthetic oil cause this will cost me a small fortune just to store it? Can I store the bike with normal oil and then refill with synthetic in the spring? Any help would be great.