Changed from Mobil synthetic gear oil to Spectro Platinum 6 speed. Mobil was an upgrade from HD. Spectro seems to be an upgrade from Mobil. Run about 2000 miles so far on it and love the stuff. Two buddies changed to it after seeing the difference in my 07 Heritage. They agree with me.Smoother shifting. Only problem is finding Spectro. Dennis Kirk discontinued carrying Spectro.It is alittle higher.But I will pay for performance.Just my opinion. Really haven't tried anything else.

 

I've been using Mobil1 VTwin 20w/50 in the engine, Mobil1 Racing 4T (10w/40) in the primary, and Mobil1 75w/90 gear oil in the transmission here in New England. All of them are available at the local auto parts stores and no problems at all.

 

Bump.

 

SPH isn't the right stuff for a Harley gearbox. I don't care how many people in the forums tell you it's the greatest stuff around. It may be good for gears but I cant see anything that thick (sticky)being good for the bearings. There's even stories starting to pop up about the 6 speeds running 140 weight having bearing issues. It may be great now but not so great 40 or 50k miles from now. A 75/90 or 75/110 is plenty for these cheesy little gearboxes. You guys that are trying to mask or hide the normal gearbox noise with super heavy fluids are not doing your gearbox any justice. But it's your bike, do what you want with it.