Shear Resistance - Delo 15w40 vs. Delo 5w-40

[Jim 5]

Originally Posted By: metroplex
Why is shear resistance a critical issue with motorcycles? Will there be significant metal wear in an air-cooled bike engine when the synthetic 5W-40 shears down?


Shear resistance is critical in bikes that have a shared sump in which the transmission gears are thought to be responsible for significant shear of the oil. Also, my bike is a known fuel diluter, so resistance to shear is also important.

Your question seems to ask why it is important for the oil to stay in the grade specified by the engineers of the engine. I know the engineers could answer that question but I take it as a given that I should try to achieve this if I have accepted their oil recommendation in the first instance.

 

[Mackelroy]

my vfr 800 tested rotella 5w40 at 1110 miles

62.7 sus 385 flash


Amsoil 15w40 gave the same metal numbers and shear numbers at 2000 miles. Identical

The ams is cheaper to run, being id have to change the rotella twice as much, for the same result.

 

[RC46_Rider]

Interesting comment/data on the Honda VFR 800.

I have the same bike and after getting a couple of UOA's back after about 2,200 miles and seeing that the Mobil 1 motorcycle oil had sheared down to a lower mid- 30 Wt. viscosity, I started thinking that the VFR engine may be hard on oil. I wonder if it is related to the V-TECH system which is hydraulic.

This summer I am going to run Delo 15W-40 and see what the UOA shows for viscosity. I have run M-1 bike oil in several bikes and types (dirt and sportbikes) and never had any lubrication problems and got good wear numbers when valve clearance was checked, but it bugged me that M-1 would shear almost a full grade in 2,200 miles, so I decided to try an HDEO and see what happens. There seem to be several reports on here that the
Rotella T-6 shears down quicker/worse than the dino 15W-40.
Starts making me wonder if the synthetics really are better....?!
Certainly this situation seems to be a negative for the synthetics on a cost vs. benefit ratio.

 

[Jim 5]

The older VFRs had timing gears instead of chains. This could be a significant cause of shear.