The most important aspect of oil flow getting to engine parts is the W rating during a cold start. The W rating was invented to ensure people use the right oil in cold weather start-ups to ensure adequate lubrication. Oil needs to get to moving parts in order to provide lubrication. Too low or no flow = inadequate or no lubrication.Over the years it was always flow=lubrication. So Toyota doesn’t want better lubrication in this case I guess.![]()
When the oil is hot, there will always be adequate lubrication, ensured by the PD oil pump. The viscosity of any multi-viscosity oil is magnitudes higher at 0C than at 100C, and the difference of 20 through 60 grade oil at 100C is small compared to the viscosity difference between a 0W through 25W at 0C.
The misnomer was "pressure = lubrication". In some cases that may not always be true. In any oiling system, if the viscosity is constant, then more oil pressure does mean more flow. But any flow above what's a totally adequate volume isn't going to make the lubrication of the parts any better. It might help keep them a bit cooler by carrying away heat.
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