Oil viscosity change for a 5.7 Hemi?

[DarkBlack]

OK, to put it in a tractor content. With mechanical pressure gauges on tractors and trucks I have seen oil pressure on the gauge before they started while cranking.

Sure, but that same pressure is there if it fires up quickly, or you continue cranking it.
That’s also only pressure in the bottom end. If you’re upper end..valve stems, overhead cams, etc, are “dry” , they’re dry either way.
Then there’s wrist pins and such, that require minimum motion speed for correct lubrication.

 

[Too many Kubotas]

Yeah, turning just the oil pump is one thing . That’s totally different than cranking an entire engine assembly with compression strokes using a starter motor.
I think people confuse the two.

I'm definitely not confusing the two.

Thankfully my batteries as good enough to turn the engines fast enough to build pressure. Not that I can monitor it on the gauges while cranking, but on the 3.6 V6s it's easy enough to hear the difference when starting them. They're noticeably quieter after having primed them.

Besides, while the starter works against the compression, the oil doesn't have to deal with the forces of actual combustion. Many Challenger owners use the starter method, but who knows, we may all be wrong by not letting a supercharged engine fire instantly (which they do) and go directly to high idle, at well over 1,000 rpm.

 

[Too many Kubotas]

That’s also only pressure in the bottom end. If you’re upper end..valve stems, overhead cams, etc, are “dry” , they’re dry either way.

Wow. So oil pressure isn't equalized in the engine, but stays pressurized only in the bottom end until the engine starts??

 

[DarkBlack]

Besides, while the starter works against the compression, the oil doesn't have to deal with the forces of actual combustion. Many Challenger owners use the starter method, but who knows, we may all be wrong by not letting a supercharged engine fire instantly (which they do) and go directly to high idle, at well over 1,000 rpm.

I didn’t know we were were talking about supercharged engines. Guess I missed that part.
The forces on the components to spin an engine at a given rpm , are closely the same, be it the crank driving the rod, or the rod driving the crank.
No free lunch here

 

[DarkBlack]

Wow. So oil pressure isn't equalized in the engine, but stays pressurized only in the bottom end until the engine starts??

That’s right. Oil to valve stems is not pressurized, and requires a minimum oil flow , and turbulence across the head, from the valve train

 

[Too many Kubotas]

I mentioned the supercharged versions as a worst case, and before that the V6.