Well first let me say this is the Best Site for info on HD's and really like the fact that everyone seems to want to help out fellow HD's riders. With that being said I have owned now 2 HD's a 02 FLHT and now a 07 RKC, really liked my FLHT but love the Road King.
Have done the Maintence by the book as far as 5,000 on the Engine (Amsoil) Trans (Spectro) Primary (Spectro) just switched to spectro and love it, Also sent Spectro a email about using just the 75w140 GL1 in the 6 speed and right from the producer said it is fine and will not hurt the bike so if any of you cannot find the 6 Speed GL-5 then the GL-1 is fine. Just wanted to get that out there. Second as far as intervals go, go by the book HD has done years and years of testing on these bikes in all types of conditions IE cold, hot, if you can think they have done it. Just go with what the book says there are bikes out there with over 150,00 on the engine and using just dino have had no problems and that is doing the changes at 5,000.
Now I do agree that if you have put the bike into a extreme situtation then if u want to change the oil by all means do it but again I am sure harley has thought of it. Talking with a Motorcycle cop they do there changes per the book, and as u know if you want extreme then they have it, and the bike purrs right along. I know the bikes are alot of money and like me I am sure u probably love ur bike more than ur wife but believe me these bikes and the way there are built are bullet proof.
Just my two cents but as long as u put a quality product in the bike Mobil 1, Amsoil, Spectro the bike will serve u well, or all this interval
(EDIT) will drive u crazy. Again one of the best sites out there and really like to read everything that people have to say. KEEP THE RUBBER SIDE DOWN!!!
A Friendly Reminder - Harley Davidson Community