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When does an engine need the most oil? #4679300
02/26/18 11:34 PM
02/26/18 11:34 PM
Joined: Jan 2007
Posts: 833
El Oeste
HawkeyeScott Offline OP
HawkeyeScott  Offline OP

Joined: Jan 2007
Posts: 833
El Oeste
Been snowed in a bit lately and have spent more time (than usual) trying to understand oil capacity and demand. Have a few basic questions:

1. When does an engine demand the most oil? I've always assumed it was at high RPMs.

1a. In a typical engine, does a pump send out more oil at, say, 5000 RPM than 4000 or is there a max output that is reached sooner?

2. In a typical engine/pan, what is the greatest percentage of capacity that is ever in use at once? For instance, in a 6 qt. system, how many of those 6 qts. are out "working" and how many are waiting in the pan to be pumped up into action? ( The origin of this question is my friend's Jeep, after his wife ran it for an extended period with only around 3 qts. in the 5.75 qt. system.)

3. Do some engine designs just require more oil to properly lubricate while in operation? I have owned the Jeep 4.0s that have 6 qt. systems, and now a 5.3 GM that also takes 6. The GM engine is about 25 percent bigger yet their manufacturers required the same amount of oil.

Thanks for enlightening me.

Last edited by HawkeyeScott; 02/26/18 11:38 PM.
Re: When does an engine need the most oil? [Re: HawkeyeScott] #4679308
02/26/18 11:57 PM
02/26/18 11:57 PM
Joined: Feb 2015
Posts: 2,595
Slovenia EU
Kamele0N Offline
Kamele0N  Offline

Joined: Feb 2015
Posts: 2,595
Slovenia EU
1) yes...higher rpms needs more oil...dont forget thst oil not just lubricates but also helps to cool down the engine

1a) not familiar about volumetric efficiency of oil pumps

2&3) look on this that way...

The more HP/litre engine has...the bigger sump it needs...add a turbo and it needs a tad of oil more...

Bigger the sump...the easier life oil will have...longer oci


2008 Toyota Yaris 1ND-TV 1.4 D4-D Elf FullTech FE 5w30
1997 Toyota Landcruiser KZJ95 3.0 TD Shell Rimula R6M 10w40
Re: When does an engine need the most oil? [Re: HawkeyeScott] #4679312
02/27/18 12:03 AM
02/27/18 12:03 AM
Joined: Sep 2015
Posts: 6,172
Kalifornia Kollective
BrocLuno Offline
BrocLuno  Offline

Joined: Sep 2015
Posts: 6,172
Kalifornia Kollective
OK, back in the day - big block Ford engines like FE's would literally starve for oil at high RPM. Drag racing would leave the pumps high and dry. Front sumps and at high RPM they filled the valve covers with oil and the pans were empty. To keep them alive you ran one qt over full. It was usually enough ... Built race engines ran restrictor orifices in the upper end lubrication

Yes, oil pumps are positive displacement. The faster you spin them, the more oil they pump.

At "normal" RPM - say 3,000 - there is about 25% in circulation. The rest is coming back down to the pan, in filtration, or the like. The reserve is there for the occasional blast to 5,000 RPM if needed (say passing).

The MFGs assume that you will be running highway speeds mostly. They give you enough reserve for passing or pulling a hill in lower gears at higher RPM. But they don't spec oiling for sustained high speed use, Except in bigger trucks and police vehicles.

The last bid spec I saw for Calif Highway Patrol is 122 MPH for one hour with A/C and full radio load at 100*F - basically desert highway pursuit. All those engines get increased oil capacity, extra oil coolers, bigger filtration - something to help...


Last edited by BrocLuno; 02/27/18 12:07 AM.

Formerly in marine engineering. In an earlier life I owned my own petroleum tank truck, and hauled for the majors and independent's.
Re: When does an engine need the most oil? [Re: HawkeyeScott] #4679315
02/27/18 12:09 AM
02/27/18 12:09 AM
Joined: Sep 2015
Posts: 6,172
Kalifornia Kollective
BrocLuno Offline
BrocLuno  Offline

Joined: Sep 2015
Posts: 6,172
Kalifornia Kollective
And KameleON is right - Oil is the number one component in cooling an internal combustion engine. It transfer heat from surface to surface so it can get to the water jacket. Like piston skirts to cylinder walls to the water jacket.

This is why we pay attention to NOACK

Last edited by BrocLuno; 02/27/18 12:10 AM.

Formerly in marine engineering. In an earlier life I owned my own petroleum tank truck, and hauled for the majors and independent's.
Re: When does an engine need the most oil? [Re: HawkeyeScott] #4679322
02/27/18 12:21 AM
02/27/18 12:21 AM
Joined: Feb 2014
Posts: 2,757
CZ factory 🏭 KC KS
Marco620 Offline
Marco620  Offline

Joined: Feb 2014
Posts: 2,757
CZ factory 🏭 KC KS
In all instances a synthetic oil or blend usually beats dino. A proper cooling system helps too. I would say a higher capacity sump or better lubricant helps. Sounds like a job for Redline Oil or Motul 300V/Neo Synthetic.


15' Civic 1.8 i-vtec 221,000 mi 0w20 Redline/Redline CVT/Archoil9100/TEIN/Eibach/Tanabe Sustec/Borla Exhaust/87 E0 fuel/Yokohama
Son of a Navy Corpsman. Support vets!


Re: When does an engine need the most oil? [Re: HawkeyeScott] #4679325
02/27/18 12:23 AM
02/27/18 12:23 AM
Joined: Jan 2006
Posts: 758
Los Gatos CA
djb Offline
djb  Offline

Joined: Jan 2006
Posts: 758
Los Gatos CA
Most automotive oil pumps are gear pumps with an adjacent pressure release bypass for regulation. They move a fixed amount of oil per rotation. When the pressure is high enough, a spring-loaded valve releases some of the flow back into the pump inlet.

This isn't especially efficient, and doesn't match the flow needs of the engine, but the simplicity and reliability of a gear pump overwhelms other considerations. If the oil pump fails, the engine doesn't just stop running, it destroys itself.

Most people think of engine oil as just lubricating the bearings. But it's arguably more important as the cooling fluid for most of the engine, and on a tight engine most of the flow is going to oil sprayers. For instance, pistons are cooled almost entirely by an oil sprayer pointed at the bottom. This need for cooling increases quickly with a heavier load, while the bearings have almost a constant flow rate independent of engine load.

Re: When does an engine need the most oil? [Re: HawkeyeScott] #4679328
02/27/18 12:25 AM
02/27/18 12:25 AM
Joined: Mar 2017
Posts: 8,173
...
PimTac Offline
PimTac  Offline

Joined: Mar 2017
Posts: 8,173
...
I learned something here. I thought the oil demand was the same regardless of the rpms but higher rpms meant faster circulation of the same volume of oil?


Cannot see signatures any longer so it doesn’t matter.
Re: When does an engine need the most oil? [Re: HawkeyeScott] #4679330
02/27/18 12:30 AM
02/27/18 12:30 AM
Joined: Sep 2015
Posts: 6,172
Kalifornia Kollective
BrocLuno Offline
BrocLuno  Offline

Joined: Sep 2015
Posts: 6,172
Kalifornia Kollective
Bearing side leakage increases with RPM.

Most engines are not squirter cooled as far as pistons go. Only expensive engines, or designs that require it.

Most everyday engines just use sling oil off the crankshaft to lube/cool cylinder walls/piston skirts.

Last edited by BrocLuno; 02/27/18 12:31 AM.

Formerly in marine engineering. In an earlier life I owned my own petroleum tank truck, and hauled for the majors and independent's.
Re: When does an engine need the most oil? [Re: HawkeyeScott] #4679334
02/27/18 12:41 AM
02/27/18 12:41 AM
Joined: Feb 2015
Posts: 2,595
Slovenia EU
Kamele0N Offline
Kamele0N  Offline

Joined: Feb 2015
Posts: 2,595
Slovenia EU
smile



2008 Toyota Yaris 1ND-TV 1.4 D4-D Elf FullTech FE 5w30
1997 Toyota Landcruiser KZJ95 3.0 TD Shell Rimula R6M 10w40
Re: When does an engine need the most oil? [Re: HawkeyeScott] #4679338
02/27/18 01:07 AM
02/27/18 01:07 AM
Joined: Jul 2003
Posts: 5,074
New Zealand
Silk Offline
Silk  Offline

Joined: Jul 2003
Posts: 5,074
New Zealand
Sweet - I always think of a splash lubricated engines when we get these complicated topics, people expounding with theory. They just need oil splashing and squirting and squishing to get the job done.


1987 BMW R65 - Aegis SAE30
2005 Nissan Expert - 5W-40 Castrol Magnatec diesel.
1996 Volvo T5 - Penrite HPR15 - 15W-60. Ryco syntec filter.
Re: When does an engine need the most oil? [Re: HawkeyeScott] #4679349
02/27/18 02:03 AM
02/27/18 02:03 AM
Joined: Dec 2002
Posts: 42,524
'Stralia
Shannow Offline
Shannow  Offline

Joined: Dec 2002
Posts: 42,524
'Stralia
Positive displacement pump shifts the same amount of oil per RPM largely. Thin oil and high discharge pressure affect that, but ignore that for the time being).

What the engine needs is more volume at high RPM, but it's not linear like the pump delivery. A pump htat delivers enough at idle delivers too much at high RPM, which is why the oil pressure goes up, and relief valves are fitted to stop the pressure going through the roof.

The modern way is variable delivery oil pumps, which deliver more flow per revolution at low speeds, and lower the delivery rate per RPM at high RPM/pressure.

Most of the heat that the engine oil has to carry away is actually generated by the oil itself shearing between the moving surfaces. The piston cooling and the like are a minor part of the overall heat that the oil has to dissipate..

Re: When does an engine need the most oil? [Re: HawkeyeScott] #4679413
02/27/18 07:49 AM
02/27/18 07:49 AM
Joined: Aug 2005
Posts: 927
dayton oh
kc8adu Offline
kc8adu  Offline

Joined: Aug 2005
Posts: 927
dayton oh
racing/track day.
high rpm and centrifugal force in the turns.
low oil level can be disastrous in a turn at redline if the oil in the pan is too low to keep the pickup submerged.

Re: When does an engine need the most oil? [Re: djb] #4679477
02/27/18 09:42 AM
02/27/18 09:42 AM
Joined: Feb 2014
Posts: 595
Margate England
Claud Offline
Claud  Offline

Joined: Feb 2014
Posts: 595
Margate England
Originally Posted By: djb
Most automotive oil pumps are gear pumps with an adjacent pressure release bypass for regulation. They move a fixed amount of oil per rotation. When the pressure is high enough, a spring-loaded valve releases some of the flow back into the pump inlet.


Most pumps are gerotor rather than meshed gear pumps nowadays. They still perform the same function though.

Claud.

Re: When does an engine need the most oil? [Re: HawkeyeScott] #4679489
02/27/18 10:02 AM
02/27/18 10:02 AM
Joined: Oct 2015
Posts: 2,930
Balearic Islands , Spain
FordCapriDriver Offline
FordCapriDriver  Offline

Joined: Oct 2015
Posts: 2,930
Balearic Islands , Spain
Overhead valve Vee engines are an example of very primitive lubrication systems that yet work quite well.
Overhead Valve V engines have their camshaft directly above the crankshaft, and the camshaft is lubricated only by the oil that slings off the crankshaft.
That is one of the reasons when breaking in an old school American V8 which has a new flat tappet camshaft, you're advised to immediately raise the revs above 2000rpm, unless you do that not enough oil will reach the camshaft nd the cam and lifters could potentially eat eachother.


1975 Ford Capri II Ghia 3000 V6, - Shell Helix HX3 20W-50 w/ 20% Rimula R4X 15W-40 HDEO.
1988 Ford Escort XR3i Cabrio, - Shell Rimula R4X 15W-40, w/ 30% Helix 3 20W-50.


Re: When does an engine need the most oil? [Re: HawkeyeScott] #4679491
02/27/18 10:04 AM
02/27/18 10:04 AM
Joined: Oct 2015
Posts: 2,930
Balearic Islands , Spain
FordCapriDriver Offline
FordCapriDriver  Offline

Joined: Oct 2015
Posts: 2,930
Balearic Islands , Spain
And yes, at high RPMS engined to like more oil.
An example is i know racers who use a whole quart/liter of oil more when on the track than on the road.
For example Small block chevrolet V8s and other overhead valve engines need to have oil flow to the top of the engine restricted to prevent all the oil going to the top of the engine at high rpms.


1975 Ford Capri II Ghia 3000 V6, - Shell Helix HX3 20W-50 w/ 20% Rimula R4X 15W-40 HDEO.
1988 Ford Escort XR3i Cabrio, - Shell Rimula R4X 15W-40, w/ 30% Helix 3 20W-50.


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