I have a 2006 FLHTC. I recently went to do a service myself now that my warranty is off and found out that they reccomend Formula Plus in my primary and tranny. After talking to one of the techs at my loal Stealer, he told me that most people are running 20/50 full synthetic fluid. I have always run the RevTek 80/90. What should I run?

 

Lots of riders use formula plus. I use Belray primary, it's an 80 wt.and in the gears I use Belray Bigtwin gear oil, it's an 85-140wt.
I think the Formula plus is a 50wt.

 

Formula + is ok for the primary but I would stick with the 80w90 in the trans.

 

I would bet there is more formula plus in primaries and trannies then all the other oils put together on newer harleys. My basis for this is that that is what harley recommends and I bet the majority of the sheep I mean people use it with good results. Literally you could probably use a stick of butter in the tranny and be okay.

 

Formula+ is OK for the primary but many better choices for the trans. Try the Spectro gear oil in the trans, you'll be glad you did.

 

+2. I use Mobile 1 gear oil in tranny. Formula + works well for me but only in the Primary.

TedMan

 

I've used 3 oils so far in my primary on my 08 FXSTC. Syn 3, Amsoil 20/50, and Formula +. Of the 3, I like the Formula + better than the other 2.