Next service is still a few thousand miles away but I want to change the engine oil over to Syn3 before winter. Should I also change the transmission and primary or is the engine oil the important one to change yearly?

 

Just follow what your manual says except for the part about using Official Harley Syn3. Everybody here disagrees about what oil is the best, but almost everyone agrees that it's NOT Syn3. Especially when it comes to the tranny.

 

+1 Formula+ for the primary. As someone said to me "you don't want anything too slick your clutch is in there. As for your trans, you need something thicker in there i.e. Mobile 1 gear oil, Bel-Ray tranny oil, Ams oil heavy duty shock proof, etc. I am a firm believer in frequent oil changes. The key to keeping a motor healthy is clean oil. I have read that syn-3 is a synthetic blended oil made by Citgo. I wouldn't use it. Reccomendations are Mobile 1 20w50, Lucas 20w50,Ams oil 20w50, etc.

 

My policy is to change oil about every 2500 miles with Mobil 1 Vtwin 20W-50. Mobile 1 Gear oil in trans and Formula + in the primary. I do the primary and trans every other oil change. That's just how I do it.

 

what weight gear oil?...I got formula + in tranny and primary...

 

Same way I had mine until I changed fluids recently. I went to Mobil 1 75w90 LS Gear oil. So far, I don't notice any real differences that I've seen stated in other threads, Maybe a placedo effect. We'll see. Also noticed some going with 75w140. I actually wasn't unhappy with Formula+ and may go back to it in the end, after I try this for awhile.

 

I cah nge my primary and tranny every 5000, i change the engine oil when its dirty. if its 1800 or 3000 when its dirty it comes out. 20/50 full syn.

 

So far, my oil that I removed has looked about as good as when I put it in. I change it every 2500 because the weather gets hot and humid and I don't want any chance of oil breakdown. Probably won't but it's cheap insurance.