Volume of oil in circulation in engine...

[geeman789]

Does anyone know roughly how much oil is in circulation, so to speak, when the engine is running. Would it be 1/2 a quart, or a whole quart, or more... or less?

Checked the oil on a friends car, and dipstick was dry... added 2 + quarts to get it full, on a 4.3 quart sump... car ran fine, no low oil pressure lights or nasty noises whatsoever.

How low can the oil level get before BAD things happen short term...?

 

[barkingspider]

Good question. My old 95 prism beater took 3.5 quarts of motor oil capacity. It was running fine. I checked the dip stick and it was dry. I added 1 full at which took it to the high full point on the dip stick. This tells me that on this car, at least one at was in circulation when running.

 

[ZeeOSix]

The level showing (or not showing) on the dipstick may also depend on just how far the dipstick goes down into the sump. In other words, there could be plenty of oil in the sump at the level below the end of the dipstick.

Only way to know how low the level was is to do like above and determine how much oil it took to get the level back on the full mark.

 

[CATERHAM]

It depends on the engine but at high rev's you're looking at about 8 gallons/minute or more being pumped through the engine.
That's a 4 quart sump being turned over ever 15 seconds or faster.
But even if you were down a quart or two I don't think you would run into oil starvation problems whereby the oil wasn't draining back into the sump fast enough to keep the oil pick-up tube covered.

Where you do run into problems is during aggressive driving; i.e., during hard cornering and braking.
Then with some cars, if the oil isn't at the full level on the dip stick you can get momentary oil starvation.
With some cars, the combination of high rev's and sticky tires requires that the sump be over filled by half a quart to a full quart to avoid the problem and even that may not be a complete solution.

 

[ShotGun429]

Around a quart is in use at any one time on a typical V8 at normal RPM's

 

[440Magnum]

Depends a lot on the engine's oiling system, of course, but I'd guess that a quart or two (not counting almost a quart in the filter) is somewhere other than the pan when the engine is running at normal operating speed.

 

[Dallas69]

A qt seems to be an awful small amount but I dont know.

 

[CATERHAM]

I once years ago wanted flush all the old oil out of an engine. After allowing the oil to fully drain in my Europa, I reistalled the drained used oil filter and added about half a quart of fresh oil and fired it up. That was enough oil to have solid oil pressure at low rev's under 2,000 rpm with the car stationary.
Of course there is already probably at least a pint of oil still in the engine that can't be drained out.
I then drained the oil again and noticed while not as clean as new, still pretty clean and not worth bothering to waste even a pint of new oil in trying to do a more "complete" oil change.

 

[MolaKule]

Originally Posted By: geeman789
Does anyone know roughly how much oil is in circulation, so to speak, when the engine is running. Would it be 1/2 a quart, or a whole quart, or more... or less?...



If you took a snapshot and froze the frame, the amount of oil in circulation after pressurization is about 1 to 1.5 quarts, depending on engine size and pump flow.

 

[Dallas69]

Why do trucks and some cars have sumps over 6 qts if less than 2 qts are in use at any given time?

 

[Clevy]

Originally Posted By: Dallas69
Why do trucks and some cars have sumps over 6 qts if less than 2 qts are in use at any given time?


How long exactly do you want the sump time to last. Smaller sump means shorter intervals as well as tougher to keep oil temps consistent.

 

[HTSS_TR]

Originally Posted By: MolaKule
Originally Posted By: geeman789
Does anyone know roughly how much oil is in circulation, so to speak, when the engine is running. Would it be 1/2 a quart, or a whole quart, or more... or less?...

If you took a snapshot and froze the frame, the amount of oil in circulation after pressurization is about 1 to 1.5 quarts, depending on engine size and pump flow.

I think it depends on engine size, a 6-7L V8 has more oil circulate in the engine than a 2L 4-cyl.

 

[zray]

Originally Posted By: Dallas69
A qt seems to be an awful small amount but I dont know.


Oil galleys are a very small diameter & bearing clearancs are pracally nonexistent in terms of how much oil is in them. A quart is estimating on the high side, not the low side.

Z

 

[MolaKule]

Originally Posted By: Dallas69
Why do trucks and some cars have sumps over 6 qts if less than 2 qts are in use at any given time?


It's called sump, "dwell time." The more oil mass you have in the sump means more of the oil mass will get more time to cool.

 

[MolaKule]

Originally Posted By: HTSS_TR
Originally Posted By: MolaKule
Originally Posted By: geeman789
Does anyone know roughly how much oil is in circulation, so to speak, when the engine is running. Would it be 1/2 a quart, or a whole quart, or more... or less?...

If you took a snapshot and froze the frame, the amount of oil in circulation after pressurization is about 1 to 1.5 quarts, depending on engine size and pump flow.

I think it depends on engine size, a 6-7L V8 has more oil circulate in the engine than a 2L 4-cyl.


Quote:
If you took a snapshot and froze the frame, the amount of oil in circulation after pressurization is about 1 to 1.5 quarts, depending on engine size and pump flow.

 

[ShotGun429]

You are Spot on Molakule!!

 

[armos]

As far as where the breaking point is:

I recall 2 incidents with family vehicles where somebody seriously neglected their oil.
In one case, a 2.2L chevy cavalier (pushrod, not the ecotec) completely seized. It was found with about 1.5qts of oil in it.

In another case, a more recent model Dodge Caravan with I think a 3.8L V6 (I don't know their engines very well) had gone very long on it's oil and had around 2 or 2.5 quarts of black syrup in it. It survived.

I wouldn't call these accurate measurements though, and obviously the way the engine is driven is a huge variable.

 

[Chris142]

A 454 holds 5 qts but grannnies northstar holds 8

 

[Michael_P]

Quote:
A 454 holds 5 qts but grannnies northstar holds 8


More cams, journals, galleries yadda yadda. I do wonder what the minimum amount of oil can be in a sump of a Northstar. I wonder if you could get away with 5 qts. I would guess so. I wouldn't be surprised if some Northstars had a 5qt sump.

 

[zray]

Originally Posted By: CATERHAM

".........Where you do run into problems is during aggressive driving; i.e., during hard cornering and braking.
Then with some cars, if the oil isn't at the full level on the dip stick you can get momentary oil starvation.


That's why there's a booming business selling racing oil pans to guys that go fast. The trick oil pans have nifty trap doors that swing open and closed to keep some oil around the pick up at all times.

Z