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[J.D.]

I've run a number of different primary oils including the Red Line MTL and "wet clutch" motorcycle engine oils.  RL seemed good and came out nice and clean but felt like it lost some clutch feel (engagement point) and seems relatively low viscosity.  Actually the 10w-40 and 20w-50 synthetic motorcycle oils felt really nice and are quite a bit less expensive (and available locally).

In my mind the oil has do not only (first and foremost) work with the clutch but also lube everything internally (chain, compensator) and protect the seals.

I generally buy it by the case and it's that time again.  What is the soup du jour?

[skratch]

well, i've been using shell rotella t 15w-40 diesel engine oil.  it is jaso rated for wet clutch use and runs about $14.00 for a gallon jug of it.  never any issue with clutch slippage or the like.  been using it for nigh on 7 years now i guess.  i have always, and continue to do so, change the primary oil every 5k miles.  same time as the engine oil.  did the clutch adjustment at the same time.  with the hydraulic clutch, don't have to adjust, but still change at the 5k interval.  i do let my tranny oil go for the full 20k.  figure if it can last over 100k in a car, then it should be able to withstand the 20k interval the hd engineers spec.

[muddypaws]

Diesel oil interesting. Can't wait to see what others think...

[J.D.]

Is that the "wet clutch" spec (jaso)?

Edit: looks like the "wet clutch" compatible spec is JASO MA or JASO MA2.  Is this correct?

[ultrarider123]

It's syn3 for me in all the holes.  Easy-peazy to find, carry a quart on trips if anything gets low and I've had no issues for many years going this route. 

[grc]

Mobil 1 Automatic Trans Fluid.  Auto trans fluids have to be fully compatible with clutches, since the average AT has several internal clutch packs.  They also have to lubricate chains and gears and operate under high heat and load conditions.

I've tried many fluids over the years and the ATF has done the best job of reducing the Harley clutch drag issue, resulting in smoother shifting.

Jerry

[J.D.]

Jerry, what do you mean by the "Harley clutch drag" issue?

Is this the oil: https://mobiloil.com/en/automatic-transmission-fluid/synthetic-atf

If so, this is very low viscosity stuff, down around Dexron VI territory.  Much lower than even RL MTL.

How is the engagement "feel" of this ATF.  Something I might be interested in trying.

[Yellow09SERG]

well, i've been using shell rotella t 15w-40 diesel engine oil.  it is jaso rated for wet clutch use and runs about $14.00 for a gallon jug of it.  never any issue with clutch slippage or the like.  been using it for nigh on 7 years now i guess.  i have always, and continue to do so, change the primary oil every 5k miles.  same time as the engine oil.  did the clutch adjustment at the same time.  with the hydraulic clutch, don't have to adjust, but still change at the 5k interval.  i do let my tranny oil go for the full 20k.  figure if it can last over 100k in a car, then it should be able to withstand the 20k interval the hd engineers spec.

I have been thinking of going the Rotella route also, there is always a couple gallons on the shelf for the truck, its cheap, and available everywhere.

[grc]

Jerry, what do you mean by the "Harley clutch drag" issue?

Is this the oil: https://mobiloil.com/en/automatic-transmission-fluid/synthetic-atf

If so, this is very low viscosity stuff, down around Dexron VI territory.  Much lower than even RL MTL.

How is the engagement "feel" of this ATF.  Something I might be interested in trying.

Yes, the official name is Mobil 1 Synthetic ATF (multi-vehicle) and it can be used in many different brands.

Many of the shifting and clunk issues with Harley transmissions could always be traced to a clutch that didn't release completely, especially the older five speed models.  I tried a lot of different lubes since 1999 to improve the issue, mostly various types of gear oils that claimed to be clutch compatible and usually in the 75w80 viscosity range. None of them seemed to be significantly better in terms of clutch performance, until I decided to try ATF.  I kept thinking about how low viscosity ATF seemed to work fine in automotive applications in not only clutch operation, but also in protecting gears and shafts as well as chains in transaxles and transfer cases.  It was used in many manual gearboxes as well.  I tried it in my bike, and immediately found it reduced the clunk on engagement that every Harley rider has complained about pretty much forever.

Give it a try and see what you think.

Jerry

[J.D.]

Thanks for the explanation.

How is the engagement "feel" of this vs. the typical primary oils?  By that I mean when the clutch starts to grab and when it is fully engaged?  What I find with most if not all of the modern "wet clutch" synthetics is the (properly adjusted and not worn) clutch seems to begin to grab when the hand lever is about 75% of the way out and fully engages pretty much when the lever is fully released.  I even upgraded the clutch release ramps to the latest updated version to help this (still using the stock/medium diaphragm spring), which it did to a certain extent, but still not the low-speed feel I'd like.

[bigskyroadglide]

I use ATF in the primary as well.  Specified by clutch manufacturer  (barnett), seemed reasonable.  Works great, never an issue.  Even have used B&M trick shift.  It works just as great as any brand name ATF.  It's blue color clearly identifies itself as the primary fluid.





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[ultrafxr]

I'm sticking with the H-D Formula +.  It's Certified-Tested by the moco and meets all their specs.  If there is ever a failure there's no warranty or ESP question.  And as an added benefit I also use it in the tranny.  That way when some migrates from the tranny to the primary I can just drain it from the primary and add it to the tranny.  EZ PZ.   

[J.D.]

How's the clutch feel of the F+ vs. something like SYN3?

How can the fluid migrate from the transmission to the primary?

[Rimjam]

ATF gets my vote, been using it for years & years.

[J.D.]

That same Mobil-1 synthetic ATF?

Just checked online; this stuff is $11/qt.  Will probably pass on it for now.