For example as for this difference, it is expressed to remarkable even in lubricating efficiency of engine top at the time of engine starting. When it is lubricating depends on just the pressure (viscosity) of the oil, when the engine stops, that pressure disappears, simultaneously the oil falls to engine lower part due to gravity. After that, the occasion where the engine re-is made to start, until the oil is sent to engine top by the oil pump, between, the oil does not exist in 2 face to face of the metal, becomes that the boundary lubricating territory appears suddenly. This it calls "dry start", it can call the most dangerous state for the engine.