The main points should be familiar to those of us who read oil papers, but I’m posting it because it’s a good paper. It’s from 2016.
The statements below are not all in the paper. Some come from other sources.
Thinner oils push the lubricant regimes to the left on the Stribeck curve. Yep, it’s still true...darn physics.
Friction modifiers help reduce mechanical friction when asperity contact occurs. Fuel economy benefits of thin oils are especially realized (compared to thicker oils) when friction modifiers are added because of the increased asperity contact caused by thin oils.
Near the top and bottom dead center piston positions are the problematic regions due to the low relative speeds there causing oil film thickness collapse. The piston rocking back and forth there makes it even worse for the film separating the piston skirts from cylinder walls. There, the shear rates are very low, so low-shear rate kinematic viscosity is the driver rather than the high shear rate like is used in the HTHS test.
The paper: https://link.springer.com/content/pdf/10.1007/s40544-016-0107-9.pdf
The statements below are not all in the paper. Some come from other sources.
Thinner oils push the lubricant regimes to the left on the Stribeck curve. Yep, it’s still true...darn physics.
Friction modifiers help reduce mechanical friction when asperity contact occurs. Fuel economy benefits of thin oils are especially realized (compared to thicker oils) when friction modifiers are added because of the increased asperity contact caused by thin oils.
Near the top and bottom dead center piston positions are the problematic regions due to the low relative speeds there causing oil film thickness collapse. The piston rocking back and forth there makes it even worse for the film separating the piston skirts from cylinder walls. There, the shear rates are very low, so low-shear rate kinematic viscosity is the driver rather than the high shear rate like is used in the HTHS test.
The paper: https://link.springer.com/content/pdf/10.1007/s40544-016-0107-9.pdf