Well I have to comment on this as well. Last time I took my bike in for the service(They gave me the 3yr service warranty when I purchased the bike),I was talking with one of the HD techs in the back. He begged me not to use Synthetic oil in the TX heat. He showed me a cup of some oill he had pulled out of another bike,not only was it black(Which means it is working),but it was room tempature and it was as runny as water. He swears the absolute best to use is regular 20-50,at least in the TX summer. I have been a mechanic all my adult life,and I have always used regular oil,and to me,oil is oil. I just put some Amsoil in my wifes Heritage,and I can honestly say that it don't seem any quieter,or cooler,or any better. Actualy,I can hear the engine noise alot clearer now. The only benefit I can see from using synthetic oils is more milage between oil changes. If oil comes out clean,even if it is lubing,it is probably not helping to keep inside engine parts as clean as it should. I pulled a small block chevy apart once because of tapping and unusual loud noises. The owner only used Penzoil,and had told me it always came out really clean looking. The cam,crank,piston rods,and rockers were all gummed up with clean looking nasty oil. The push rods were so bad that no oil could even get through them. Just my opinion,from the old school,when I change the oil again,I will go back to regular 20-50 oil. If it ain't broke,don't fix it. Here in TX with the temp reaching 107 degrees today,I don't need the oil to start out thin and runny.