Not trying to create a maelstrom, but...

IF MoCo recommends a 20W-50 lube in all three holes, then why aren't more folks using Mobil 1 V-Twin 20W-50 in their transmissions?

A quick look at some numbers indicates that Mobil 1 V-Twin 20W-50 compares very favorably to Mobil 1 LS 75W-90:

Mobil 1 V-Twin 20W-50 Oil
Viscosity Index 142
Pour Point -42
Flash Point 214

Mobil LS 75W-90 Gear Lube
Viscosity Index 142
Pour Point -39
Flash Point 150

Just sayin'...

 

You'd be better off using the automotive version in two of the three (everything but the clutch). The friction modifiers will fight wear in the engine and transmission. Preferrably a 15W-50.

Save the motorcycle formulation for the transfer case.

 

You could and it would be fine in all likely hood. I would not because the numbers you listed do not tell the whole story. I use Mobile 1 15-50 in the engine and I use a gear oil in the trans. The reason I use a gear oil in the trans is because of the extreme pressure additives used in gear oil. In my research and understanding, motor oil has additive packages meant for the motor and gear oil has additive packages meant for the trans. But hey, it is a free country and it is up to you. As I stated earlier it will probably be fine.

 

Moco dont recommend, they say you "can" but they ship the bike w gear oil, so thats what I use...
jmo.

 

You can manually add powdered Molybdenum Disulfide to the transmission's oil to take care of the extreme pressure role, while avoiding the more corrosive aspects of some gear oils. That said, our transmissions don't really deal with high-pressure sliding situations--not like hypoid, bevel, and worm gears do, which is what the high pressure additives like ZDDP and MoS2 are designed for.

 

The Mobil 1 V Twin 20w50 is fine for all 3 holes. Says so right on the bottle and I'm sure they know a little more about oil than we do. I would say there are some better alternatives for the tranny to make it quieter but I have known people that have ran the Mobil 1 in all 3 holes without any issues.

 

it's a go in my book. 20W50 has the same viscosiy as 75W90 gear oil and 20W60 has the same viscosity as 75W110 Gear oil.

 

If the MOCO says you can use Syn 3 20-50 in all 3 holes then I don't see why you couldn't use Mobile 1 20-50.

 

20-50 is fine imho. I get slightly better shifting and can find neutral easier with a syn. gear lube tho.

 

same here. I use Lucas syn gear oil.