Shearing = shift quality degradation... ?

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I have read almost every thread discuss how shift quality deteriorates over the course of an OCI. Is this directly caused by the level of shearing an oil experiences? Or is there something else at play?
 
This has been the case for many years with shared sump bikes/quads. I've dealt with it for a long time in just about every make and model. My current '11 KingQuad 400 shears oil fast and gets very notchy within 500miles. My 08 Kawasaki Ninja 650 does also when using the recommended 10W40 lube. I even went with some Castrol 10W40 full syn this time and it lasted longer but still gets very notchy after 1000 miles or so.
 
In which case your viscosity choice should compensate for 20-30% shearing in a shared sump if you want to maintain decent shift quality for the majority of the OCI.

Or... use an oil that doesn't shear... which is rare.
 
Yes as oil ages in a shared sump motorcycles the polymer VII are sheared or cut by the mechanical action of the gears. This causes the viscosity to drop and the gear change to go bad. Notchy at first, but soon you end up missing gear changes or requiring a lot of boot to get it into gear.

I tend to run thicker oils so they shear into grade after 1000 miles, rather than out of grade.
 
My 1998 Honda VFR 800 shifts fine throughout the 5k mi OCI. I've been using Mobil 1 5W-40 Turbo Diesel Truck that I got on clearance at Auto Zone. Once that's gone I'll use the Pennzoil Platinum Euro 0W-40 I got on clearance at WalMart.
 
Originally Posted By: SR5
Yes as oil ages in a shared sump motorcycles the polymer VII are sheared or cut by the mechanical action of the gears. This causes the viscosity to drop and the gear change to go bad. Notchy at first, but soon you end up missing gear changes or requiring a lot of boot to get it into gear.

I tend to run thicker oils so they shear into grade after 1000 miles, rather than out of grade.


This is what I'm thinking with the recent purchase of Valvoline 20w50.
 
Originally Posted By: Joshua_Skinner
My 1998 Honda VFR 800 shifts fine throughout the 5k mi OCI. I've been using Mobil 1 5W-40 Turbo Diesel Truck that I got on clearance at Auto Zone. Once that's gone I'll use the Pennzoil Platinum Euro 0W-40 I got on clearance at WalMart.


Your bike doesn't require Jaso spec oil?
 
any type of oil using a smaller spread will use less VII that shear, an oils first # besides the cold flow is what base oil is used before adding VII so a 15-40 is inherently better than 10-40's + the quality of the VI's are many. cheap oil cheap polymers aka VII. of course you must consider riding temps as well!!! true synthesised synthetics are far better requiring very little VII + generally last longer if you don't mind paying $10+ a quart, of course there are other benefits as well. those that DIY can easily change their oil sooner + be better protected + have better shifting. rotella T 15-40 a cheaper conventional diesel oil is quite popular for that reason !!!
 
Originally Posted By: webfors
Originally Posted By: Joshua_Skinner
My 1998 Honda VFR 800 shifts fine throughout the 5k mi OCI. I've been using Mobil 1 5W-40 Turbo Diesel Truck that I got on clearance at Auto Zone. Once that's gone I'll use the Pennzoil Platinum Euro 0W-40 I got on clearance at WalMart.


Your bike doesn't require Jaso spec oil?

Most bikes run fine with diesel oil. No "Energy Conserving" on diesel oil so no clutch issues.

I run Peak 15w-40 syn blend diesel oil in my bike, and have used Supertech 15w-40 as well.
I am just starting to notice some notchiness in shifting and difficulty finding neutral @ 2200 miles on the oil, so will be changing it soon.
 
No shifting degradation ever experienced in both of my bikes (see my signature) using motul oil only.uoa showed pretty decent sharing also in both of them. Never felt any difference during the interval or after changing the oil (which I did about 15 times in 85.000km total)
 
Originally Posted By: Panos
No shifting degradation ever experienced in both of my bikes (see my signature) using motul oil only.uoa showed pretty decent sharing also in both of them. Never felt any difference during the interval or after changing the oil (which I did about 15 times in 85.000km total)


So that's interesting.. because your UOA showed significant shearing, yet you noticed no difference in shifting quality..
 
Originally Posted By: webfors
Originally Posted By: Panos
No shifting degradation ever experienced in both of my bikes (see my signature) using motul oil only.uoa showed pretty decent sharing also in both of them. Never felt any difference during the interval or after changing the oil (which I did about 15 times in 85.000km total)


So that's interesting.. because your UOA showed significant shearing, yet you noticed no difference in shifting quality..

Some bikes are not as susceptible to shifting problems from shearing as other bikes.
 
That's also my conclusion after reading and hearing so many reporting shifting quality difference. At the same time , very few people I know or post here seem to use the motul brand.
 
Originally Posted By: Panos
That's also my conclusion after reading and hearing so many reporting shifting quality difference. At the same time , very few people I know or post here seem to use the motul brand.


I've tried most brands out there over the years, and Motul 300V 4T is my favorite. The bikes run great, and shift perfectly for the entire OCI. I've tried numerous HDEO's, and the shifting always quickly degrades in my bikes.
 
Originally Posted By: Panos
That's also my conclusion after reading and hearing so many reporting shifting quality difference. At the same time , very few people I know or post here seem to use the motul brand.


Problem with Motul is cost and availability. I'd try it if it wasn't $20/quart and only at select bike shops.
 
Last edited:
Originally Posted By: webfors
Originally Posted By: Joshua_Skinner
My 1998 Honda VFR 800 shifts fine throughout the 5k mi OCI. I've been using Mobil 1 5W-40 Turbo Diesel Truck that I got on clearance at Auto Zone. Once that's gone I'll use the Pennzoil Platinum Euro 0W-40 I got on clearance at WalMart.


Your bike doesn't require Jaso spec oil?


The first JASO spec was, from what I can find, introduced in 1998. My motorcycle, developed before JASO oil standards, does not specify a JASO oil.
 
I'm kind of hijacking this a little, but can anyone speak about what happens to the oil at low temps when the oil shears?
 
Generally the low temp viscosity also suffers from shearing. Unless the polymer has an abnormally high low temperature viscosity, it aids the fresh oil in staying fluid at low temperatures. So as it shears, it could decrease its ability to do so. It kind of depends on the polymer used though.
 
The only two oils I have used that don't degrade shifting during an OCI are Motul 7100 and Maxima Extra 4. Rotella 15w40 has started out notchy in three bikes in which I have tried it.
 
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