Fluid Clarification
My name is Chris and I'm a newcomer to the forum, as well as to the Harley-Davidson realm. I beg your forgiveness in advance for my resulting naivety, but I'm curious to know which fluids should be used for the primary and transmission fluids in a 2018 Milwaukee-Eight 107 softail Harley-Davidson.
I have done a lot of "Googling" and found a lot of conflicting information. As a result, I figured I would find a Harley-Davidson forum and seek the wisdom of experienced owners. To be clear, I'm not asking about what brand I should choose and I certainly don't want to do everyone a disservice and start a conventional vs. synthetic war. I'm merely looking for the types of fluids required.
I know that the engine oil should be a 20W-50... that much is pretty clear. But I'm a bit hazy on the Primary and Trans.
I look forward to reading and learning lots from you folks.
Thanks in advance.
Last edited by InfiniteGlide; Jul 6, 2018 at 12:35 PM.
My name is Chris and I'm a newcomer to the forum, as well as to the Harley-Davidson realm. I beg your forgiveness in advance for my resulting naivety, but I'm curious to know which fluids should be used for the primary and transmission fluids in a 2018 Milwaukee-Eight 107 softail Harley-Davidson.
I have done a lot of "Googling" and found a lot of conflicting information. As a result, I figured I would find a Harley-Davidson forum and seek the wisdom of experienced owners. To be clear, I'm not asking about what brand I should choose and I certainly don't want to do everyone a disservice and start a conventional vs. synthetic war. I'm merely looking for the types of fluids required.
I know that the engine oil should be a 20W-50... that much is pretty clear. But I'm a bit hazy on the Primary and Trans.
I look forward to reading and learning lots from you folks.
Thanks in advance.
So:
Engine: 20/50
Primary: Formula +
Transmission: RedLine Shockproof

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Bike comes with HD 20W50 in the motor and HD Formula+ in the tranny and primary. At first service I'll probably do what I do on all my bikes. HD Syn 3 in the motor, Belray 85W-140 gear oil in the tranny and HD Formula+ in the primary.
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Using conventional oil apparently does quiet V-Twin engines. I suspect this is at least partly because conventional oils all contain some trace wax left over from the refining process whereas synthetics contain no wax whatsoever. I eschew the use of waxy oils in the interest of engine sound quality and have instead installed RockOut rocker lockers which quiet the V-Twin a great deal. You should look into these and not compromise on oil IMHO, but thats just me. Redline also offers a 20/60 oil for use in very hot conditions.
RedLine oils are excellent full synthetic oils which use Esters as their base oil. Likewise Mobil, Royal Purple, Amsoil and others are full synthetics using PAO's in their base. Beware of cheaper, so called, synthetics particularly if their proprietary formulas are so friggin special they'd have to kill you if they told you what it was. These are probably what are called group III synthetics which are in fact highly refined conventional oils and not really synthetic at all. Not that these are bad oils but I have issues with product stating "Synthetic" on the can not having synthetic in the can, again, thats just me.








