Are viscosity requirements or specifications based mostly on oil temperature or bearing clearances? Or something else?
Simple question?
- Thread starter ledslinger
- Start date
- Status
Both and it seems that a lot of motors have had the viscosity thinned for fuel economy as well.
Expected oil temps, clearances, required oil pressure, fuel economy, engine design and metallurgy, expected usage, sump size, desired oil change intervals, market availability, commonality with other cars, etc. etc....
The oil is specced together with all of those things. They affect oil choice and vice versa.
For example, BMW designs their oil specs to run long OCIs and take a fair amount of abuse. At the same time, they design most of their engines to use the same oil spec. Mercedes and Porsche do the same thing.
The oil is specced together with all of those things. They affect oil choice and vice versa.
For example, BMW designs their oil specs to run long OCIs and take a fair amount of abuse. At the same time, they design most of their engines to use the same oil spec. Mercedes and Porsche do the same thing.
Bearing clearances have not changed much in the last 40 or so years. Mains are usually in the .0025 range and rods are .0015. You cant get much closer than that.
Bearing clearances have not changed much in the last 40 or so years. Mains are usually in the .0025 range and rods are .0015. You cant get much closer than that.
So since bearing clearances haven't changed, and viscosity specs have gone down, oil temps are now lower. Or viscosity was already above what it needed to be.
So since bearing clearances haven't changed, and viscosity specs have gone down, oil temps are now lower. Or viscosity was already above what it needed to be.
Variable camshaft timing that operates using oil pressure and passages sometimes require certain weights.
Originally Posted By: ledslinger
Or viscosity was already above what it needed to be.
Bingo
Or viscosity was already above what it needed to be.
Bingo
Originally Posted By: ledslinger
So since bearing clearances haven't changed, and viscosity specs have gone down, oil temps are now lower. Or viscosity was already above what it needed to be.
Base stocks are better so they don't shear down with use or thin out as much when hot. Also, since combustion is cleaner and more efficient, oil doesn't have to deal with as much contamination.
So since bearing clearances haven't changed, and viscosity specs have gone down, oil temps are now lower. Or viscosity was already above what it needed to be.
Base stocks are better so they don't shear down with use or thin out as much when hot. Also, since combustion is cleaner and more efficient, oil doesn't have to deal with as much contamination.
- Status