I an Airplane mech and I highly recommend you get a sample kit from
http://www.blackstone-labs.com/what-is-oil-analysis.php or a sismilar one and check your oil through them. Use an independant lab, not one like AMmsoil etc as they just try to sell their product. My most recent one said, Wow, Quite a bit of metal in oil. Recommend you change it sooner, could be just breakin or beginning of a problem. Do'nt use additives or products that promise renewal. If they did what they promised, we would'nt wear out engines. If the products are so great, why are they not apprved by the FAA?