Lighter weight GL5s for Manual Transmissions?

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Looking to start a list and conversation of GL-5 rated gear oils that may be suitable for manual transmissions containing hypoid differentials (i.e. Subarus). I'm specifically interested in choices lighter than 75w-90 (less than 14 cSt@100C and ideally less than 80 cSt@40C), as I'm thinking this may help with drivablitiy issues, and there seems to be very little available that fits the bill.

Going off of MolaKule's list (fantastic resource) and what I could dig up on my own I see:

Liqui Moly Gear Oil (GL5) 75W-80
-Viscosity at 40°C 52.3 cSt
-Viscosity at 100°C 8.5 cSt

Fuchs TITAN SINTOFLUID SAE 75W-80 synthetic MTF
-Viscosity at 40°C 49.8 cSt
-Viscosity at 100°C 9.4 cSt

Subaru Extra MT 75w-80 (only available in 5gal)
-waiting on viscosity info

Motylgear 75W-80
-Viscosity at 40°C 58.8 cSt
-Viscosity at 100°C 10.1 cSt

Ford XY-75W85-QL Synth Hypoid Gear Lube (no LS FM?)
-Viscosity at -40°C 48,000 (no 40°C spec found)
-Viscosity at 100°C 11.5 cSt

MOTYLGEAR 75W-85
-Viscosity at 40°C 82.6 cSt
-Viscosity at 100°C 12.6 cSt

RAVENOL MTF-1 SAE 75W-85
-waiting on viscosity info
-unsure if LS friction modifiers are included

Motul GEAR 300 75W-90 (incl. because of exceptional low temp viscosity)
-Viscosity at 40°C 72.6 cSt
-Viscosity at 100°C 15.2 cSt

Redline 75W90NS GL-5 (incl. for comparison):
-Viscosity at 40°C 90.4 cSt
-Viscosity at 100°C 15.6 cSt

Thoughts?
 
I've got Redline 75w90 NS in my Subaru now for about the past 25k miles. It shifts smoother than anything else I've had in the trans (5MT). Sure, when the temp is below 0*F the shifter can still be a pain to get into first gear the first shift of the day and until about 5 miles into the drive while rolling, but there is no grinding on any shift, even the ones that make the rubber rear diff mounts hate life. I don't have the specs like the other ones but you can find them.

Gear 300 actually was tougher to shift when cold in multiple gears and da^n near impossible to get into first when subzero.
I would also not recommend "Uncle Scotty's Cocktail" as that was actually the hardest to live with, at least for my tranny. Stiff when cold, would frequently grind 3rd gear.
 
I'm going with the 75W90NS Redline in my 08 Legacy GT, along with 1 qt of the heavy shockproof just for added measure. I hear nothing but good about this combo and its not really a "cocktail" like the original Scotty's formula that mixed all sorts of fluids.

I have Valvoline 75W90 GL-5 in it now (for the past 20K) and it sucks. No grinds really, just notchy and hates going into first unless you are completely stopped.
 
Originally Posted By: BrocLuno
You did not include Redline MTL, or I misread the list ...


MTL isn't going to be GL-5, its a GL-4. I'm not aware of many transmissions that REQUIRE a GL-5, and relatively few that even ALLOW a GL-5 fluid. Obviously there are Subies, but the majority of lubricants specifically tailored to manual transmissions are going to be GL-4 AT MOST, and many won't have a GL-x rating at all. People that have to have a GL-5 due to hypoid gears sharing the same sump as the synchronizers are going to be, inherently, much more limited in fluid choices than people who don't have hypoid gears running in the same lubricant as the synchros.
 
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Sorry, but as a Subaru owner you have to put up with the cold balky shifts. In the world of MT they aint that bad. This is NORMAL MT cold weather operation FWIW.

Make sure you hydraulic linkage is air free and well enough off the floor. Most shift concerns are due to poor linkage adjustment.
 
Originally Posted By: 440Magnum
People that have to have a GL-5 due to hypoid gears sharing the same sump as the synchronizers are going to be, inherently, much more limited in fluid choices than people who don't have hypoid gears running in the same lubricant as the synchros.


Hence the reason for the list. Any I’m missing?
 
What you need is Subaru Hyperformance Gear Oil for the common sump that carries the GL-5 rating.

The only other MTF 75w90 I am aware of is the Ford XT-75W90-QGT which carries a GL-5 rating as well.

Plain Jane hypoid GL-5 rated differential fluid is usually too high in viscosity and does not have a friction Modifier for the synchro assembly.
 
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