I just purchased a 20/52 Fastrak and want to replace my filter/oil in the first 5 hrs. The Honda manual mentions nothing about the use of synthetic oil. Obviously, I don't want to do anything to void my warranty, but have always thought that using synthetic can only extend my engine life. Does anyone have any advice/thoughts on the subject? BTW, I visited this site numerous times prior to purchasing my Fastrak and found it helpful and, in fact, a major factor in deciding to go forward. I'm having so much fun and waiting for the grass to grow!