Greetings All!

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.

 

Haven't bought a new bike in awhile so don't know what comes with them anymore but didn't your bike come with an owner's manual? If it did, it should tell you in there.

 

Do check your manual. Aside from that, HD recommends HD products. If you wish to stick with that then HD's Formula + in the primary is just about a sure bet and you can probably use it in the tranny too. I'd opt for a dedicated gear oil for the tranny if it were me. I use Redline Shockproof in my 103 TC trnsmission. Its very popular but expensive. HD was recommending their pseudo synthetic Syn 3 in all 3 holes for awhile. If that works, anything will.

So:

Engine: 20/50
Primary: Formula +
Transmission: RedLine Shockproof



.

 

Sadly, it didn't. Had to order it.

 

Okay, so I'd been planning on using Mobil1 Fully-Synthetic 20W-50 in all three holes. But perhaps I need to re-think that approach. Thank you.

 

Pretty much anything on the primary, I use rotella T4 15w40 & many like redline in the tranny. I use belray big twin transmission fluid & it works great too & only about $12/qt. Running belray mineral 20w50 in the motor. 103" TC

 

Mmm, I've read accounts where people have sometimes experienced clutch slippage using certain synthetics in the primary though, somewhat oddly, others using the very same product don't. In most cases those with slippage problems found the problem went away when they switched to Formula + and thats why I recommended it to the OP. I use RedLine in all 3 holes, 20/50, V-Twin Primary, and Shockproof in the tranny. RL's V-Twin primary is synthetic but is friction modified to (supposedly) prevent clutch slippage. Its one of the oils which doesn't work for everybody but it works for me just fine. Anyhow, though I'm sure there are plenty of different oils used in primaries, as there are in the other holes, it may not be a slam dunk that "anything goes" for certain machines, at least. Just sayin.

 

I have an '18 FXLR, mine came with an owners manual. 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.

 

what are your thoughts on the redline 20w50? Full synthetic? I was thinking a conventional oil would quiet down the twin cam like it did in my intruder 1500 but it's just a noisy motor apparently. I think I need a synthetic in the AZ heat.

 

I like the fact that RedLine makes a product line specific to V-Twin (3 hole) engines. RedLine's 20/50 V-Twin oil, though not unique among MC oils in this aspect, is high in ZDDP too. ZDDP reduces engine wear but has been reduced in "automotive" oils to preserve catylitic converters. This is why I prefer MC specific oils over automotive oils in general. Synthetics are generally more temperature stable too, meaning they need less of the added long chain polymers, which are subject to shear, than conventional oils require in order to produce multi-grade properties. RedLine, being Ester based, is slightly superior to other synthetics in this regard.

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.