Is there a best time to switch to synthetic oil? I've heard that you can use it in a brand new bike from day one. I've also heard wait until 4000 miles or so, until the engine is "fully" broken in before switching to synthetic, and everything in between! I tend to believe that you can use it from day one, since several bike/car manufacturers use it as their factory fill, and other than the ring/cylinder seal, today's engines don't need thousands of miles to break in, like they used to in the past. Am I correct?