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
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.
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.
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
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?
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
"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
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."
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
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
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
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.
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
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
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.
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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