buy your oil from Wal-Mart...an interesting oil essay...

[GreekGod]

http://www.boss302.com/oil.htm

[JMan]

GG,
Great read! Thanks for finding this.

J

[ckadiddle]

I understood about 30 percent of it....heehee I will keep changing oil about every 300 miles.

[RF Overlord]

That was one of the few oil articles I've read where the author actually DOES know what he's talking about.

Thanks, GreekGod. :up:

[Ross]

Now wait a minute. That article says that it takes about five minutes for the oil to start being pumped up into the upper engine. Can this be right? It takes that long, and all of that time the only lubrication that the upper engine gets is whatever is left clinging to the parts from the last time the engine was started? That sounds like an awfully long time to me, but then, I ain't no engineer.

[GreekGod]

Now wait a minute. That article says that it takes about five minutes for the oil to start being pumped up into the upper engine. Can this be right? It takes that long, and all of that time the only lubrication that the upper engine gets is whatever is left clinging to the parts from the last time the engine was started? That sounds like an awfully long time to me, but then, I ain't no engineer.

What he said:

When your engine is first started, this 'Static' layer of protection will give the engine adequate lubrication for a few minutes (5 or so) until the oil pump has the ability to create enough oil pressure to get the heated oil moving up into the upper parts of your motor.

[Breadfan]

Yeah, and those with "real" oil pressure gauges on their Marauders can basically see when the engine oil reaches it's operating temperature. I don't romp on mine until I see this through the gauge. It takes atleast that long, maybe longer!

[Ross]

OK, I'm still confused, as usual.
Does this mean that in the first 5 minutes, cold oil is being pumped up into the upper engine?
Or does it mean that in the first 5 minutes, NO oil is being pumped up into the upper engine since it's not heated yet?

[RF Overlord]

I think the author meant that you don't get full flow to the heads until the oil is at least partially warmed up. There IS flow, just not a lot, and it is definitely a good idea to be easy on the car at least until the coolant temp gauge starts to rise above C(old). I won't go anywhere near WOT until the temp gauge reads normal.

This is what happens when I skim through an article... :rolleyes:

[Joe Walsh]

I'm not in complete agreement with that statement either...

Your Oil pump is a gear pump...a positive displacement pump.
It is pumping the same amount of oil with each revolution whether the oil is ice cold or red hot.
The oil can't recirculate back through the pump...There is nowhere for the oil to go once it is pumped but through the oil passages which eventually lead to the cylinder heads and valves.

Now, when the oil is cold it is thick and hard to pump, hence the 65-70 psi my Marauder's real oil pressure gauge reads at idle with a cold engine.
When the oil is warmed up my gauge reads @ 15 psi at idle.

The author, no doubt, knows a LOT more about this subject than me, but I think that his '5 minute' statement is ambiguous and a little misleading.

He states "for a few minutes (5 or so) until the oil pump has the ability to create enough pressure to get the heated oil moving into the upper parts of your engine"....huh?
The oil pump creates oil pressure almost immediately upon engine start.
If it didn't we all would have wasted cam bearings, worn valve guides, and gauled rocker arms within a few thousand miles.

[GreekGod]

...part of the oil pump output is bypassed when oil is cold.

[Vortech347]

Nice writeup. I won't buy a damn thing from walmart...

[Ross]

With my admittedly limited understanding of the oil pump, I always thought exactly what JoeWalsh said. Sounds very logical to me. That's why I was confused about the "5 minute" part of the article. Just didn't make sense, but then, I'm married and a lot of things don't make sense to me...:shake:

[Canadasvt]

Nice article. One good thing about my old Honda Civic was that the oil was up there in the upper regions right away.
Let's not get confused with oil press and oil temp. With my SVT Focus the oil pressure was there after start up, but in the winter months I could drive over 15 miles and still the oil temp would be dead cold.

[RF Overlord]

hence the 65-70 psi my Marauder's real oil pressure gauge reads at idle with a cold engine.
When the oil is warmed up my gauge reads @ 15 psi at idle.Joe, if you have the real working version of the AutoMeter gauge, you might want to look into replacing the sender. Back when we first discovered that the factory gauge was fake, most of us who replaced it got closer to 100 lbs at cold start and 25 lbs at idle when hot. Zack got the same readings as you, but his sender later failed and when he put the new one in, he got the same readings as the rest of us.

[Dragcity]

I suspect he meant to say 5 seconds or so.

That was a long article, lot's of thoughts going throught the writers head, 5 minutes/5 seconds.... Easy to do

[jonroe]

I wonder if my sender is having a problem. When first installed a year or so ago I would be just under 100 when cold and right at 25 when hot. Cruise was about 60 or so. Now, cold is about 90, cruise about 55, and hot idle at 20 or below. All readings are just a little lower than when the sender was new.

[Breadfan]

I wonder if my sender is having a problem. When first installed a year or so ago I would be just under 100 when cold and right at 25 when hot. Cruise was about 60 or so. Now, cold is about 90, cruise about 55, and hot idle at 20 or below. All readings are just a little lower than when the sender was new.

Sounds OK.

Just curious, what oil do you use?

[Joe Walsh]

Joe, if you have the real working version of the AutoMeter gauge, you might want to look into replacing the sender. Back when we first discovered that the factory gauge was fake, most of us who replaced it got closer to 100 lbs at cold start and 25 lbs at idle when hot. Zack got the same readings as you, but his sender later failed and when he put the new one in, he got the same readings as the rest of us.

:hmmm:

My real gauge has always had psi readings in the range that I stated....

Can it fail, yet continue to give psi readings...albeit low psi readings??

Also, I've got a rebuilt forged engine with billet oil pump gears...maybe looser clearances than OEM engines?

:dunno:

[RF Overlord]

Joe, that's exactly what happened in Zack's case...his readings were lower from the time he installed the replacement gauge & sender until his sender failed entirely, but if you've got a built motor then your readings may be accurate. I didn't mean to confuse things, I just wanted you to know about the "normal" pressure readings on a stock motor.

Interesting case in point: the 60kW emergency generator at one of the telecom sites I'm responsible for has a 5.4L Ford SOHC motor and it makes oil pressure of almost 100 lbs when started cold, but settles to around 72 lbs after warm-up...it runs at 2650 RPM, so I don't have an "idle" reading, but it's interesting that the cold-start reading is so close to the number I get in my MM.

[GreekGod]

from the 2003 shop manual, page 303-01B-5:

Oil Pump...

...System pressure is limited by an integral, internally-vented relief valve which directs the bypass oil back to the inlet side of the oil pump...

...The relief valve calibration protects the system from excessive pressure during high viscosity conditions...
------------------------------------------------------------------------

also, hot oil pressure @ 1500 rpm is spec'd 138-319 kPa (5W-20 synthetic bend)

[Joe Walsh]

from the 2003 shop manual, page 303-01B-5:

Oil Pump...

...System pressure is limited by an integral, internally-vented relief valve which directs the bypass oil back to the inlet side of the oil pump...

...The relief valve calibration protects the system from excessive pressure during high viscosity conditions...
------------------------------------------------------------------------

also, hot oil pressure @ 1500 rpm is spec'd 138-319 kPa (5W-20 synthetic bend)


:hmmm:

I wonder how much of the pumped oil gets recirculated during a cold start-up...and how much gets pumped to the upper engine...?

[GreekGod]

...I'm thinking the 5 minute warm-up time would apply when it is below 20 degrees F, and certainly below 0 degrees F.

These engines are incredibly tight- clearance specs:

intake stem/guide, .00078" to .00272" (real world, 1 to 3 thousandth inch)

exhaust stem/guide, .0018" to .0037" (real world, 2 to 4 thousandth inch)

piston/cyl bore, .0003937" to .0010236" (real world, .4 to 1 thousandth inch)

connecting rod bearing/crank, .00106" to .00272" (that's 1 to 3 thousandth inch)
-----------------------------------------------------------------------
No wonder they spec 5W-20W oil!

[MENINBLK]

...I'm thinking the 5 minute warm-up time would apply when it is below 20 degrees F, and certainly below 0 degrees F.

No 5 minute warm up here...
I start the engine and let it idle for about 30 seconds.
Drop it in D and then drive off.

The highway ramp is 3 blocks from my house.
At 55 MPH it takes 3 miles to bring the engine to operating temp,
and I have absolutely no problems with my engine.