You will get lots of answers. Harley SYN3 was named this to go in all three holes. Good reading on Harley-Perfomance.com. I like their reasoning AMSOIL 20W-50 in crank case, 10W-40 in primary and Severe Gear Oil 70W-90 20in trany. I won't go through all the why, read for yourself then decide, but that is what I am doing. Have to admit, seems to me 20W-50 should be OK for all but tranny.

 

MountainCruiser provided a very good reference, www.harley-performance.com. I read a good deal of the voluminous info there. It did note that Amsoil had benefits over SE Syn3.

In just the few responses to this thread thus far, there are obviously varying opinions regarding the appropriate fluid for each hole.

Something else to consider:

According to the HD maintenance schedule for the 2012 Heritage, the crankcase oil should be changed every 5000 miles, the primary fluid changed every 10000 miles and the tranny fluid changed every 20000 miles.

What do you feel is more important; the fluid used for each hole or changing the fluids at the appropriate intervals?

If I changed the crank oil every 5000 miles, how many miles would it take for me to identify changes in the engine using Syn3 versus Amsoil? Same for primary? Same for tranny?

 

I've tried several in the first 15k as per dealer instructions.. Hd oil, Hd SYN3, HD Formula+, Belray, and finially Mobil 1 SYN.

then I Tried,,Mobil 1 V twin 20-50 in Engine and Pri.. and Mobil 1 75-90 GFL and I totally like and I am pleased with it.

IMO its the best of all the oils that I've tried and used Plus its easy to get and most auto stores have it on sale every spring, so I usually get enough for 2 changes..

I've also read one shouldn't use oils if its over 3yrs old,,???? just saying if true, don't buy 10yrs worth of it..



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