[GrandSport]

Originally Posted by blsfrs

Don't put your crayons away just yet.

I understand that with higher temperatures there is a decrease in pressure due to the decrease in viscosity.

Is there a corresponding increase in flow?

And, I'd still like to understand the drop in pressure from 4k to 7k rpm with higher temperatures.

You're going to hit mechanical limits of the oil pump at a certain point (rpm), is my guess. It's going to be "volume flow limited." Same volume, lower viscosity, lower pressure, lower mass flow. The volume flow will certainly be constant for a given RPM across each "test."

BTW: with all this said, PRESSURE and not mass flow is important for oil because its oil pressure that keeps the rod bearings from rubbing on the crank. Flow and pressure are obviously related (Pressure = flow * resistance), but you can pump as much oil as you want- if there isn't pressure (force) to push back on the rod bearings, you'll have contact.

Oil doesn't so much "lubricate" rod bearings as it does keep the separate. It lubricates contact surfaces like rings/walls, camshaft lobes, etc.

Using fluids is a buffer, the same but different, is used in after burners. They burn at 4000 degrees. You know what doesn't burn/melt at 4000 degrees? absolutely nothing useful. But air still has to be ducted (and in the case of the F22, trust vectored). Imagine 4000 degree exhaust gas temps. What the hell do you do?
They push a layer of cold bypass air through thin little holes (that some super smart dude figured out where to put and how many to put in) so they get a near perfect laminar sublayer of air between the exhaust flap and the hot air. Effectively, it creates a buffer between the hot air and the exhaust flap. You can see the little holes and slits in the hot side of the convergent/divergent flaps
https://qph.cf2.quoracdn.net/main-qi...2dcc0148b17255