Originally Posted By: Gokhan
Originally Posted By: Clevy
Originally Posted By: Gokhan
OP has forgot that in addition to cold starts, idling is also very bad for your engine. Idling is bad because the oil film thickness increases with RPM. Speed and viscosity is what keeps moving parts from making metal-to-metal contact.
His main concern was that with thinner oil engine turns faster and this may result in more wear. On the contrary, slower the idle speed, more is the wear on the engine. You still don't want to race a cold engine over 3000 RPM but faster idle is actually better than slower idle as far as wear is concerned because the oil film between the moving parts will be thicker with more RPM.
Wouldn't this just apply to bearings or is this true for all the lubricated components?
It's true for all components. Look at the Stribeck curve. Even in the boundary-lubrication, mixed-lubrication, and elastohydrodynamic-lubrication regions, you reduce friction when you increase speed, which means you move away from metal-to-metal contact. Put a block of metal on a oiled metal surface and there will be metal-to-metal contact (the dot in the graph below). However, if you push the block and give it some speed, it will start lifting off from the surface -- just like ice skating. Note that the valvetrain uses boundary as well as elastohydrodynamic lubrication.
Now that's very interesting indeed
Thank you very much
Would anyone care to add anything relevant here or is this pretty much got it?
Thanks again.