Greetings all. I have been told that I need to run a synthetic oil in my son's XR350R, and was hoping someone could reccomend one that I can run in both that bike and my XR650L. I've heard that one cannot use synthetic to break in a motorcycle. Since I'm going to be breaking in my '650L, I need to confirm or dispell this rumor. The XR350R seems to be nearly stock, having only an aftermarket air filter. My '650L has alot of modifications. Another question: Will jetting a tad rich make a bike run cooler? What about running a high octane fuel? I'm determined to take good care of the '350R, and have been warned about that model and year having horrible overheating problems. Thank you all for your input, I appreciate it greatly.