oil presuure

94 chevy 3/4 ton during first start up oil pressure is good. after 1 hr of driving, pressure is way low. Check gauges comes on, oil level is good. changed oil an filter an oil sending switch. but no improvement. is my oil
pump slowly going out.
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It is a PITA...but check Op with a mechanical guage to see if you really have a problem.

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Wise idea also in a older high mileage engine like that stop using 5w30 now if you are still using it as it will boost oil pressure. Use a minimum of 10w30. ----------------- TheSnoMan.com
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At operating temperature, there is no difference in the viscosity of 5w30 and 10w30.
Maybe suggest straight 40 in summer and 10w30 or 10w40 in winter....depending on where he lives.
wrote:

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On Fri, 20 Oct 2006 23:48:33 GMT, "News Skimmer"

In theory yes in the real world no. In order for a oil to pass a 30w rating it is tested to be in a certain viscosity range at 200F (at 0F for 5w and 10w rating). They do not test it at 230 or 240 or 250 and more that oil can easily get in engine bearings with a engine running 190 to 200 (figure on at least a 50 degree rise from pressure and shearing of oil in journals even more under a heavy load) 5w30 Dino oil has a LOT more VI (Viscocity Improver) which is a polymere based additive that does not add to lubrication qualities of oil at all and it becomes unstable at higher temps and oil thins out even more as the polymere looses its abilty to make the thin base stock "thicker" at high temps. 10w30 is made from a heavier base stock to begin with and has less VI and is a lot more stabile oil under higher temps. High VI content also has a nasty habit of cooking out in pistons rings and causing them to stick if oil is left in too long or engine runs hot a lot (Saturns have a nasty habit of this in older models because GM temp management can let engine temp to get to 230 and more before it even engages cooling fan). Ford wisely uses 5w20 (not that I like 20w in a hot engine) that has a lot less VI in it and is more stable at higher temps and has less tendancy to cook out in rings. If you scan news groups and forums you will find a lot more GM vehicals with sticky ring complaints than Ford and you will find that basically every GM car that has this problem has had 5w30 or 10w40 in it. Bottom line you will see 5 to 10 PSI more oil pressure in a hot engine with 10w30 than 5w30 as I have seen this in MANY engines. Myself I do not use 5w30 unless it is going to be extremely cold a lot (like 15 or 20 below or colder) BTW GM started spec 5w30 in late 80's because they determined that at minus 20 it provided marginally better lubrication for flat tappet hydraulic lifters on cam lobes but guess what, they have since switched to roller lifters and this is not longer a issue but they stay with 5w30 becuaese it is thinner at higher temps and can provide fractionally better MPG in theory at the expense of reduced surface oil film thickness and strength to rupture and over all wear protection because a thinner oil will tolerate less microscopic grit that filter passes which increase long term wear potentail. But this is good for GM because they want you to buy another car and they do not want it to last too long anyway as there in no profit in cars that last a very long time. ----------------- TheSnoMan.com
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Uh-oh...
Snojob doesn't like it when facts get in the way of his dogma.
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On Sat, 21 Oct 2006 02:24:39 GMT, aarcuda69062
Nopeople like you that do not understand how and why things work or the effect of high VI content in oil has on a oils high temp performance makes such stupid comment because they do not even know how oil is even tested or grade either. But what is the surprize because you are here to start truoble not to learn ANYTHING or help. ----------------- TheSnoMan.com
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So, you understand that the oil viscosity will fall within the range of 9.3 to 12 .5 centistokes when it is at 212* F but somehow fall way below that range if it's heated anywhere above that temperature. Boom! just like that, they all thin out!
I think I'll pass on your understanding which is nothing but a generality.

It is clear that what you -think- you know about motor oil was learned a number of decades ago making it totally useless and irrelevant. You mention "shear" at high temperature but make absolutely no mention of centipoise numbers.

There is scant little I could learn from you since your idea of teaching is to give erronious and inaccurate information.
Okay, go ahead and teach us...
Q1) What is the viscosity difference between a 0W oil and a 5W oil at 0* F?
Q2) Where is the knock sensor on a Dodge Ram V-10 engine?
Q3) What fitting would one utilize in order to measure the fuel pressure on a common GM truck throttle body injection unit after the injector but before the fuel pressure regulator?
Q4) Is there a viscosity difference between a 10W30 and a 10W40 oil at 212*F?
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On Sat, 21 Oct 2006 15:09:35 GMT, aarcuda69062

But do you understand that most 5w30m barely fall under 30 rating in thickness and that the high VI content that makes it possible subtracts from oils lubricating properties? I think not . Nor do you understan how high VI contain oils are more unstable at higher temp in engine bearings and result in lower oil pressure.A 5w30 SYN does not rely on VI and acts a little differntly but 5w30 is loaded with VI and unpreditable at best as tempature climbs and hours wrack up, 5w30 dino is made off or a much thinner base stock than 10w30 is and it shows up in oil pressure in a hot engine big time. VI may modifiy the flow test results but it reduced film rupture strengh, part protection and high temp stabilty too. But then if you realy knew have of what you claimed to know you would know this. Time for you to go back to google to look up some stuff to do damage control and to try to make yourself look good. ----------------- TheSnoMan.com
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"Thickness?" Popular term at the lumber yard.
Anyway, a XW30 motor oil can test at 9.3 centistokes or it can test at 12.5 centistokes, or it can test at any point in between. Specifically, which is it that you're referring to when you say "barely?"

Which group of base stocks are you referring to?

No surprise here.

Folks, what Snojob is describing here primarily applies to worn out engines, something that he is indeed an expert on.

Since the FTC now allows that oil made from Group II, Group III and Group IV base stocks to be marketed and labeled as "synthetic," your blitherings are pretty much irrelevant. (not to mention incoherent)

"and hours wrack up" Like past its service life? Question 5) What is a 'tempature?"

None of which fall under the definition of viscosity.

"have of what you claimed?"

Hate to tell you but, it's not 1983 anymore.
So, as far as the four questions , I'll put you down for a "I don't know."
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On Sat, 21 Oct 2006 22:16:51 GMT, aarcuda69062

You mean your skull right?

Pretty dense arn't you?

Yes not surprizes with your responces

No what ding a ling is doing is trying to CYA. You will get lower hot oil pressure with 5w30 dino oil vs 10w30 and you can take that to the bank. Ding a ling has no clue what polymere VI additives do to oils actual lubrcatinf property or rupture and shear strength. No surprze though

Are you trying to impress some one? I do not know who.

Again, such a loon

Maybe it your book dummy, but a thinner less viscoosous stock is used for 5w30 and it is modified with a high VI conent (about 3 to 4% by volume) to make it look like 30 but it is not nor will it protect as well because as stated earlier VI has zero lubricating properties itself

I claim nothing, I tell it like it is while you tell it like you think it is but your are wrong as usual.

I hate to tell you that you can not become a rocket scientest via google but you think you can. Guys like you are dangerous because you read a little and then think you are a expert. You have a real ego problem.

Yes I do agree you realy do not know but will never admitt it. Time for you to go back the google to try to save face again. ----------------- TheSnoMan.com
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No, I mean "lumber yard."
The only "thickness" one might associate with motor oil would relate to the dimensions of the bottle it comes in.

Snojob has no answer (again).

Oh, I dunno... I can spell 'aren't' correctly.

Do you mean "responses"?

Then explain for us why it is that the oil pressure on all three of my vehicles measures exactly the same when hot no matter whether I use 5W30 or 10W30, and why that exact same phenomenon can be and has been observed by numerous people on numerous vehicles as tested by GM, Ford, Chrysler, Toyota, Nissan, Subaru, Isuzu, etc, etc, etc.?

No, I'm trying to establish how there can be any fact to your above comments regarding "A 5w30 SYN and viscosity improvers when there is no legally defined definition of synthetic motor oil and as such, your claim that "5w30 SYN does not" can not possibly be true.

Awww... Poor Snoball.

Thinner is for weight loss plans and lacquer paint jobs.

Hooked on phonics?

All nice and long winded, but it has nothing to do with the viscosities of 5W30 and 10W30 motor oil at 212* F being the same.

You're too stupid to get it.

How did mankind survive for millions of years before you caame along?

"Rocket scientest?"

Projecting.
Guys like you are dangerous because you have access to usenet.

The questions were for -you- to answer. Funny, hardly a post goes by that you don't have an answer for. Your silence at this point is quite telling.
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wrote:

Wow. Can he really be real? I think more trollish every day.
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ok pressure is good. truck is running good. oil level is good, gauge says low. now when ever i sit at idle. gauge reads maybe 2 or 3 psi. give it some gas and it rises to 30 then drops back down to 2 or 3. i check oil lines, wires for resistance. everything checks out. whats next dropping oil pan to inspected???????
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