Engine oils

Bking:
I know this sounds daft but oils have a higher viscosity when they are hot eg 10w /40 is thicker at 80 degrees than at 20 due to binders in the oil. The idea is that when an engine is cold its easier on the starter to turn the engine over also the oil puts less load on the pump and lubricates journals etc quicker.
The first viscosity number is when the oil is cold (20 degrees ) and the second number is at 80 degrees.
The oil appears to be thinner at high temperatures but it “sticks” to bearing surfaces longer.

Yep, sounds daft…for a very good reason.