I have been very happy with Amsoil. In my truck, quads that I race, and now, as of today at 3000 miles in my Harley. I believe it may be due to the filter. I know HD filters, as stated before have the drain/or bi pass. Ive read articles that say use whatever oil, etc. They recommend using a HD filter. We shall see what occurs utnil my 5000 service or after, thats if I dont by a 2011 bike.