The OEM rod bearings debate

[SmsAlSuwaidi]

Not to jack and jump in this discussion but can you guys expand on the reason for 0w-20 and how does it affect bearings and clearance ?

[Calum]

Originally Posted by SmsAlSuwaidi

Not to jack and jump in this discussion but can you guys expand on the reason for 0w-20 and how does it affect bearings and clearance ?

I'll take a crack at it.

Viscosity is a fluid's resistance to flow. The higher the viscosity the higher the resistance. As the clearances get tighter the oil will need a lower viscosity inorder to properly flow around the bearing. And, if the clearances weren't tight enough, the oil might flow out of the bearing too quickly. 0w-20 has a significantly lower viscosity than 5w-30 or 10w-30 so it should be used with tighter clearances. By using a lower viscosity oil the motor will run a little more efficiently as the pumping losses are lower, and everything else seems to have been made to suit that lower viscosity.

[OrbitalEllipses]

Originally Posted by Calum

I'll take a crack at it.

Viscosity is a fluid's resistance to flow. The higher the viscosity the higher the resistance. As the clearances get tighter the oil will need a lower viscosity inorder to properly flow around the bearing. And, if the clearances weren't tight enough, the oil might flow out of the bearing too quickly. 0w-20 has a significantly lower viscosity than 5w-30 or 10w-30 so it should be used with tighter clearances. By using a lower viscosity oil the motor will run a little more efficiently as the pumping losses are lower, and everything else seems to have been made to suit that lower viscosity.

And let me put my hat in; you want a quality oil additive package and viscosity such that the shear strength is high. When the oil shears, it loses viscosity and no longer does the job it's supposed to do. That is basically the oil debate as it will continue for eternity.