I too am struggling with this. I going too run SYN3 in Motor and Primary and run 75-140 in trans.

 

Run anything you want, as long as you change it regularly. I have an 07 Ultra with 111,000 on it and have ran synthetic, dino, semi-synthetic. Whatever is on sale. Change it every 5,000 miles - no problems. I am in Florida so that involves a bit of riding in the heat here and there as well.......

 

Synthetic will last 20000 miles, so they claim. If you're going to pay all that money for it why not let go. Me, I will sick with good ol dino, and be able to retire from my job 5 years sooner with all the money I save.

 

I use the synt due to the high temps here and heavy traffic

 

Here's my take;
If ya ride every day and put put a load of miles on it syn CAN be worth it. If I were able to do that i would extend change intervals out to what a used oil analysis would recommend.
To me, thats the only way to justify the cost of syn.
I've run both, had UOAs on both. Was told with the syn I could extend to 10000 miles on engine oil, but to watch for fuel in oil (common for all air cooled engines) so i may NOT have reached 10000 miles.
The UOAs on dino oil (Castrol GTX 20-50) showed all was well at 5000 miles. So I stayed with dino oil.

 

It's my bike and I choose to run Amsoil in it.

 

You can also do some research and read some of the other eleventy million threads on the subject. I'm not being an ***, really, there are some darn good arguments for and against. I remember one of the posters was some kinda chemical engineer and did a whole breakdown of temp to viscosity to mileage and some other stuff that I didn't understand. I use Synth cuz thats what they put in on my first oil change and now they say I can't go back to dino. So thats my reason.

 

There will always be those that have a different opinion,that's Okay.Been using synthetics in everything we own including all our compressor's for well over 30 yrs.Saves big money on wear and tear as well as time spent just changing oils every 3K.It has to mean enough to look into it no matter what the critics have to say.

 

Dino oil is for cheapskates....proven fact.

 

+1 on that. Got dino in my bike right now and I am damn sure a cheapskate!!