If I'm not mistaken (and I don't believe I am) Amsoil Motor Oil meets API Gl-1 requirements, which as shown below is for "Light Duty Requirements"..

I prefer to use a API GL-5 rated Gear Lube (and not a GL-1 rated motor oil) in the manual transmissions of my cars, trucks, and yes, even my Harley's...

(Mobil 1 75W90 Gear Lube is a synthetic fluid with a API GL-5 rating, and if formulated for Heavy Duty/Severe condition in transmissions and other gear applications.)


API classification subdivides all transmission oils into 6 classes:

API GL-1, oils for light conditions. They consist of base oils without additives. Sometimes they contain small amounts of antioxidizing additives, corrosion inhibitors, depresants and antifoam additives. API GL-1 oils are designed for spiral-bevel, worm gears and manual transmissions without synchronizers in trucks and farming machines.

API GL-2, oils for moderate conditions. They contain antiwear additives and are designed for worm gears. Recommended for proper lubrication of tractor and farming machine transmissions.

API GL-3, oils for moderate conditions. Contain up to 2.7% antiwear additives. Designed for lubricating bevel and other gears of truck transmissions. Not recommended for hypoid gears.

API GL-4, oils for various conditions - light to heavy. They contain up to 4.0% effective antiscuffing additives. Designed for bevel and hypoid gears which have small displacement of axes, the gearboxes of trucks, and axle units. Recommended for non-synchronized gearboxes of US trucks, tractors and buses and for main and other gears of all vehicles. These oils are basic for synchronized gearboxes, especially in Europe.

API GL-5, oils for severe conditions. They contain up to 6.5% effective antiscuffing additives. The general application of oils in this class are for hypoid gears having significant displacement of axes. They are recommended as universal oils to all other units of mechanical transmission (except gearboxes). Oils in this class, which have special approval of vehicle manufacturers, can be used in synchronized manual gearboxes only. API GL-5 oils can be used in limited slip differentials if they correspond to the requirements of specification MIL-L-2105D or ZF TE-ML-05. In this case the designation of class will be another, for example API GL-5+ or API GL-5 LS.

API GL-6, oils for very heavy conditions (high speeds of sliding and significant shock loadings). They contain up to 10% high performance antiscuffing additives. They are designed for hypoid gears with significant displacement of axes. Class API GL-6 is not applied any more as it is considered that class API GL-5 well enough meets the most severe requirements.

 

Nah, nobody around here has any special preferences when it comes to oil.

 

Yes, AMSOIL 20W-50 meets API GL-1. H-D's own Screamin' Eagle SYN3 full synthetic 20W50 also meets API GL-1 requirements, which it too can be used in both the engine and the tranny. It is my understanding that an API GL-5 or a GL-4 is used for shaft drivin gears, axles, etc.

From Mobile 1's web site...

75W-90

"Not recommended for automatic, manual or semiautomatic transmissions for which engine oil or automatic transmission fluids are recommended."

 

And Harley no longer "Recommends" a Motor (engine) Oil in the Sportster Primary/Tranny. The recommendation is for their Formula+ which is a Gear Oil. The MoCo only says it's OK to use a Motor Oil in the Primary/Tranny, and that comes on the heel of their failed campaign to try and convince people that "One Oil in All Holes" was a good thing.

 

this is only about the seven hundredth time we have been thru this but what the hell, here we go again!

 

The effect of the spAmsoil, White Paper cult, lives on.

 

Then someone should tell them that because they are still marketing their SYN3 as a all in one oil. I'm not saying it's a good or bad oil (I dont use it) I'm just saying.


For me I prefer not to run a passenger vehicle weight gear oil in a Sportster.


To the OP...
As you can tell we all have our favs. And I'm not gonna say anyones wrong for running what they think that should. As long as your not running vegetable oil in the engine and WD-40 in the tranny!

 

Sorry, but you, like many other people, simply do not understand the differences between Motor Oil and Gear Oil. If you examine the chart below, you'll see that Motor and Gear Oil viscosity is measured on two different scales, and that in fact, a 20-50 Motor Oil is basically the same viscosity (weight) as a 75-90 Gear Oil. I won't even bother to get into the differences between the additive packages that go into the 2 different oils, other than to say that Motor Oil contains an additive package designed to deal with the by-products of the combustion process, while Gear Oil contains an additive package designed to deal with molecular shearing that occurs in a gear box.

 

Perhaps I don't. But you still ride a GIRLS BIKE!! HA take that!!

 

You're right. I forgot that I was in the girls,,,,,,,,,,,,, err Sporty section, and not many of the females here have a mechanical aptitude.