What Primary Oil is your Choice

[bax467]

i dig my redline mtl. gives much better clutch feel than the grabby 'ol formula plus. before i was always thinking my clutch needed adjustment. now, despite the weather and how long i've been in stop and go, it stays ultra consistant.

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[aeproberts]

I am a noob when it comes to Harleys. I have a Sportster, and in my case the primary and transmission lubes are the same correct?

[Gary7]

Originally Posted by aeproberts

I am a noob when it comes to Harleys. I have a Sportster, and in my case the primary and transmission lubes are the same correct?

Yes, the primary and transmission on Sportsters share a common sump and use the same oil. This limits your choices. You don't want to use a GL-5 gear oil, and you don't want to use ATF. Harley's Formula+ is probably the best all around fluid for the Sportster transmission.

[OldFenderGuy]

As far as the combination primary/tranny on the Sportsters, many that I know (including myself) run the Mobil 1 75W90 gear lube without any problems at all.

Some of these bikes have well over 50,000 miles on the ticker, and no one has experienced any problems at all with the clutch pack.

Mobil 1 75W90 synthetic gear lube does have a API GL-5 rating.

Also, many think that 75W-90 gear lube is much to "thick" to use in a primary, but as you can see from the below chart viscosity of motor oil and gear lube is rated differently.

75W90 gear lube has about the same viscosity (thickness) as 20W50 motor oil.

[Gary7]

Originally Posted by Gary7

With a VI of 139, a vis at 100C of 20.0 cSt, and a pour point of -60F, this is a synthetic fluid, I don't care what Harley says. There is no way you can make an oil with those specs from even the best Group II hydrocracked base oils. It has to have PAO in it.

The specs I listed above have circulated on the Net for quite some time as being the "official" specs for Formula+ as published by the MoCo. This past weekend I conducted a freezer test on Formula+ and several other fluids, including motor oils, gear lubes and ATFs. After 12 hours at 0F Formula+ was opaque and would just barely pour. This tells me that pour point of -60F is total baloney, which may mean the rest of those specs don't apply, either. The fact that Formula+ turned opaque and almost solidified at a measly 0F tells me this is a conventional fluid made from Group I base oil. The PAO based 75w140 gear oil was still crystal clear after 12 hours at 0F and would pour easily. (And that's what's in my transmission now.)

It's no wonder the clutch is so grabby with Formula+ at cooler temps. I'm dumping it out of my primary next chance I get.

[Gary7]

Originally Posted by Vagabond

Any one ever hear of this?

http://www.harleyhelp.com/oilbrand.html

It's a good thing he put that nonsense about synthetic oil and "bearing skate" down toward the bottom of the page or I would not have read most of his web site. What tripe.

[old skool1983]

got amsoil in both holes in the sporty, come the summer i will be switch it gear lube for the primary since its connected to the tranny and it gets hot as haties down here in FL during the summer

[garyhendley]

amsoil 20/50 works great in the primary-ride safe

[Gary7]

B&M Trick Shift is what's in my primary now. No more jump when you put it in first cold, and hot shifts are like butter. Nice linear clutch engagement, too.

[eagle56]

Whats ATF like will it hurt my 08 fatboy .
Its embarassing have to freewheel it beore selecting 1st when cold to stop the heart stopping clonk