[bwilson4web]

Many of us have known for years that Prius brake pads and shoes last a very long time. This is due to regenerative, gentle braking and driving so we don't have to brake. But it takes energy to remove brake pad material. A lot of energy and wasted heat and the same thing happens when we wear away the engine and transaxle parts.

Ordinary lubricants try to seperate the moving parts by a thin layer of oil. But when that thin layer is compromised by fine particles or inadequate viscosity, the highest parts of the metal surfaces friction weld, momentarily and then break off. This forms the fine, less than 10 micro sized particles that like smoke, drift off and contaminate the oil. These are detectable in the rates of wear metal contamination.

A viscous oil also robs power by 'stiring losses'. Take a bowl of water and stir it at a fixed rate, it will warm up as the mechanical force is converted to waste heat. Then fill the same bowl with grease (aka., Crisco) and stir it at the same rate and the greater, viscosity resistance will warm and even melt the grease (best done with a kitchen mixer.)

So we have two forces and the challenge is to find the optimum mix of two competing forces: viscosity vs wear.

I do not have an answer but the first part of finding an answer is to understand the problem. So let me restate the problem in the extreme:

• sacrificial surfaces - in this mode, the viscosity is so low that the surfaces are like brake pads, always being sheared down.
• suspended in grease surfaces - in this mode, the surfaces never touch as the oil layer keeps them apart but absorbs the energy in heating the oil (or lubricant)
• sacrificial = suspended loads - in this mode, the heat from shearing the surfaces matches the heat lost in stirring the viscous lubricant

I don't know the answer but I think i finally understand the problem.

Welcome to my world,
Bob Wilson