Time required for oil to circulate in an engine

[CATERHAM]

How much time does it take for oil to circulate in a typical modern passenger car engine?

Is there a formula for this based on rpm?
I'm going to guess a 10 cSt oil at 100C will take say 30 seconds to circulate (from the pick-up point in the sump back to the sump) at 1,000 rpm and 5 seconds at 6,000 rpm. How far off am I?

Lighter oil circulates faster than heavy oil or does it? Rather, wouldn't there be a kinematic viscosity point at which a lower viscosity reaps no further gains in flow?

 

[Quattro Pete]

I would expect it to be much faster than that, but that's just a wild guess.

 

[hate2work]

As long as we're guessing, I'm gonna say around 6 seconds cold and 4 seconds warm.

 

[Gary Allan]

Depends on the pump volume. 5gpm is peak for many engines. But I don't think you're asking how long it takes for the full sump to cycle, I think you're asking how long any amount of oil is outside of the sump.

That would be hard to figure ..but does cause me to recall one football punting statistic that was either interesting on unnecessary depending on who was asked. Hang time.

 

[CATERHAM]

Max' pump volume does shed some light on it.
Is 5gpm, 5 grams per minute?

 

[Rand]

gallons?

 

[Nick R]

Originally Posted By: CATERHAM
Max' pump volume does shed some light on it.
Is 5gpm, 5 grams per minute?


Gallons lol.

 

[38sho]

Originally Posted By: Gary Allan
Depends on the pump volume. 5gpm is peak for many engines.



get some real engines!

from ford:

3.0L Taurus SHO yamaha DOHC v6
oil pump flow 12.15 gallons per minute @ 6400rpm's...... thats not even redline, lets think about 7200rpm's, or even 8000 rpm's.........

so 12.15 gallons is 48.6 quarts, I take a 6 quart capacity......


it pumps my oil capacity completely 8.1 times in a minute at 6400rpm

or roughly every 7 seconds

 

[beast3300]

That's a mean oil pump^^^^^

 

[hooligan24]

what is the filter rated for on that taurus?

 

[Nik]

Oil pump is a gear pump and it always pumps constant volume for a given rpm i.e. Flow = const. x rpm

so it really doesn't matter if the oil is cold or not, unless the pumps is warn out and then spins oil inside of it's casing.

 

[SpitfireS]

Originally Posted By: Nik
Oil pump is a gear pump and it always pumps constant volume for a given rpm i.e. Flow = const. x rpm

In theory

Google some volume-flow/rpm charts of industrial gear pumps and you will find that gear pumps only give a constant volume per rpm in a certain rev range, most not even above 3k rmp.
And with a constant viscosity fluid (water).
Engine gear pumps have a huge rev range to cover and have to deal with a changing fluid.

 

[Gary Allan]

Originally Posted By: 38sho
Originally Posted By: Gary Allan
Depends on the pump volume. 5gpm is peak for many engines.



get some real engines!



Get some typical engines

Even my HV pump is only rated @ 9gpm @ (something like) 3500 rpm. The engine itself can only process about 5gpm @ a spec'd weight. I'm speculating that the rpm limit is due to the actual pump design outlet port size. At some point it would provide enough restriction to attenuate the flow due to internal pressure limits.

 

[mechtech2]

This aspect of an engine does not mean too much to me.
[Unless someone measures their oil life in minutes, not thousands of miles.]

 

[dnewton3]

Originally Posted By: hooligan24
what is the filter rated for on that taurus?


If it's the 3.0L old Yamaha top end product, as I recall it used a FL400S? I used to own one of those cars, but cannot remember for sure. Equivilant to the Wix 51516?


On the topic of flow, most positive displacement pumps are a fairly linear delivery rate, except at the extreme ends of pump speed. Going well below or above the designed operational rpm will skew the performance. But overall, the rate is fairly linear.

 

[Geonerd]

Also remember that most pumps have a blow-off valve that kicks in when the oil pressure reaches a certain point. I suspect most engines reach this pressure somewhere near the middle of the the rev band, naturally depending on oil viscosity/temp, filter pressure drop, etc.

I'd make a WAG that the average car pumps 1/2~1 GPM at idle, and peaks near the 5 GPM several folks have quoted. (I seem to remember my Honda pumping around 5 or 6.)

 

[CATERHAM]

Thanks for the inpuy guys.

One of the reasons for posing the question had to do with heat transfer to the oil. Since at maximum flow the oil is circulating through an engine very quickly. Conservatively speaking, the volume of a typical 4 quart sump is pumped through an engine every 12 seconds. That provides little time for much heat transfer on a single pass or cycle; I'm thinking maybe one degree?
That being said, the oil in the hottest part of the engine and the coolest (the bottom of the sump presumably) would not differ much in temperature when the oil is flowing anywhere near it's maximum rate; a few degrees at most?

Opinions?

 

[mechtech2]

CATERHAM - You are forgetting that most of the oil in the crankcase is splash lubricating the pistons, cam[]s, etc. There is a LOT of contact with hot surfaces, and this lets the oil draw heat away from surfaces.
What is pumped through the oil passages is trivial in comparison.
It is as important as the cooling system.

 

[Gary Allan]

Quote:
Conservatively speaking, the volume of a typical 4 quart sump is pumped through an engine every 12 seconds. That provides little time for much heat transfer on a single pass or cycle; I'm thinking maybe one degree?


The higher the flow rate the higher the heat rejection. The thing is the higher the flow rate in an engine, the higher the thermal input. It's not like you've got a flow that's independent of the heat producing element. Your combustion rate and btu content will dictate your oil temp. At least when indexed for the rejection rate at the moment.

In my non-exchanged observations, you would reach some stable temp on the highway and you could drop 10F+ with just taking your foot off of the gas pedal. There you just unmasked the rejection rate by eliminating the high combustion pulse thermal input rate.

Under that stable loaded state to an unloaded state, the average return temp was 10F+/- less. I'm sure that it was a composite of higher and lower temps from various contact points....the pistons probably contributing the highest thermal content per volume ..or so I would reason.