I have heard it said that a Jaso bike oil lacks certain friction modifiers....Ok... but are there any addtives put into it to to enhance clutch action? And does the oil change with use so it becomes less friendly to the clutch?
T4 15w40 has been the go-to of all of the Rotella oils for decades.
T6 5w40 is known to have low shear resistance (poor shifting after a while) because of the high amount of viscosity index improver needed to bridge the gap from 5 wt to 40 wt.
T4 is absolutely acceptable for a shared sump as he specifically mentions the clutch and how shift quality degrades some oils the longer they are in use. It's a simple matter of shearing in the gearbox and not necessarily related to anything with the clutch being able to grip. Shift quality and clutch slipping to me are two totally separate things. And T4 is known for good shear resistance and no issues with clutch slippage.
The holy trinity of science is 1)Reason 2)Observation 3)Experience...
employing those tools we observe that the chief cause of clutch slip
are high mileage... mileage is the constant among all of the clutches
that begin to slip... oil choice whether JASO approved or not is not a
constant... High mileage is the constant where all clutches begin to
loose grip due to normal glazing and contaminates that build up over use...
Originally Posted by Truckedup
I have heard it said that a Jaso bike oil lacks certain friction modifiers....Ok... but are there any addtives put into it to to enhance clutch action? And does the oil change with use so it becomes less friendly to the clutch?
In 2006, MA1 and MA2 were added as extra categories within the JASO MA specification. The main difference between these two categories is the higher friction performance MA2 oils are delivering. This meant that from 2006 on, motor oils that meet the T903:2006 standard can be divided into four specifications for 4-stroke motorcycle oils:
JASO MA: This is the standard specification for oils that are used within one oil system (where the engine, gearbox and clutch use the same oil). These oils don't contain any friction modifiers.
JASO MA1: This is a lower standard specification for motorcycles that require different oils for the engine, gearbox and clutch.
JASO MA2: This is a higher standard specification for modern motorcycles. These oils are suitable for use in motorcycles that have catalytic converters in the exhaust system.
JASO MB: This is a lower standard specification for scooter engines.