Why is viscosity important in motor oil for today’s high revving engines?

Why is viscosity important in motor oil for today’s high revving engines?

If the oil in your car is has too little viscosity, it will easily flow out of the gaps between surfaces and will not lubricate them well. Those surfaces will experience sliding friction and wear. If the oil has too much viscosity, it will waste the engine’s energy by opposing motion and turning work into thermal energy. Modern motor oils have carefully adjusted viscosities that balance the two problems. Since temperature affects viscosity (e.g., hot molasses has less viscosity than cold molasses), motor oils add chemicals that stabilize their viscosities over wide temperature ranges.

Does air create a friction force on water? Would a gutter be much quicker at hav…

Does air create a friction force on water? Would a gutter be much quicker at having water flow through it, rather than a pipe?

Air does exert frictional forces on water, but much less than a surface would. Thus a gutter would be a better water carrier than a pipe. It would have one less surface to slow the flow of water.