Motorcycle gearboxes create a shearing effect that causes permanent oil viscosity loss. When this happens there is permanent loss of the oil's ability to prevent metal to metal contact.

From the above graph you can see that the other two oils under test quickly become borderline 30 weight oils even when one of them starts off significantly thicker.
Amsoil is totally sheer stable.

With AMSOIL MCF, there is no need for separate* transmission lubricants. It is absolutely shear stable and will not thin out from mechanical activity. AMSOIL MCF performs like a gear lube without the negative effects of extreme pressure additives.

*Most motorcycle engines & gearboxes are common so separate transmission lubrication is NOT a choice.

In the FZG gear test, AMSOIL MCF achieved a perfect score with a “zero” wear rating (see photos below).

FZG Gear Test (ASTM D-5182)

LOOK what happens when the going gets tough, like this viscosity measurement at 150 degrees C / 302 degress F.

- This temperature is reached in HOT running air cooled motorcycle engines -

This dramatic eye popping lab result shows BIG differences in the one measurement you need the most to protect your engine when it gets hot. Remember, this measurement compares NEW oils to each other. Choose the wrong oil and your high temperature viscosity protection is lacking, right out of the can!

Down the road there's the real world possiblilty your 10w-40 oil of choice breaks down even further now becoming a 30wt (or even less) as the first graph shows! Now that your 10w-40 oil of choice is a 30wt oil what's left of it's wear protection capability at the high temperatures air cooled motorcycle engines reach so easily?