So ever since I've had my current road bike, the rear wheel has made a slight rubbing/off noise periodically while free spinning. It is barely noticeable. Now that I'm finally maintaining my own bike, I determined that the noise seems to be coming from the freehub - more noticeable when the freehub is attached to the wheel. The LBS mechanic told me to squirt some tri-flow into the freehub and spin it up. This seemed to help out a little, but it is still there. I'm guessing tri-flow wasn't the ideal lube since it is pretty thin - but it's not like you can squirt grease into the freehub. I have no idea how to service a freehub - but would be willing to learn if necessary (and if possible). The mechanic seemed to indicate it wasn't a big deal - had no impact on performance. Should I just leave as-is?