mcodecuda
Senior Member
Finally, someone that understands oil ratings.
How quickly should oil pressure come up?
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I understand totally. I chose not to argue. Oils do not change viscosity. Period. I'm still not going to argue, as that's not what the discussion is about, but I suggest you do some reading on the subject.
Phreakish
Well-Known Member
Let others argue for you:
What Exactly Do The Multi-Visc Designations Mean?
The whole of human knowledge at our fingertips and yet old wives tales persist...
A 10w-40 and a 10w-30 might be the same when cold, they might not (usually not). We'd need a ton more info to know for sure but in most cases the 10w-40 will always be slightly thicker, it'll just have some more or higher grade viscosity improvers to get the hot viscosity higher. But how it's measured cold and how it's measured hot are different and the ranges that qualify for 5/10/15w are pretty wide.
Dave999
Well-Known Member
its oil flow that counts
i have the joy of 265 6
same pump internals as the 273 318 etc
shifts a lot of oil as flow, never impresses with pressure , does on occasion take a while to show pressure on start, 7 main journals to feed mind.
my sender is electronic the reading on the gauge seems to depend on how much sealer you use, that messes with the earthing
if there is some flow you are unlikley to hang up a bearing at idle regardless of what the gauge says. Your starter is punny in comparison to the forces created by combustion.
next time pump is out check cover for scoreing and clearnce between impellor/clover leaf and cover.
if you spot obvious change at rpm when hot say from 60PSI to 30PSI, when 60 is what you have routinely seen...then worry...its very hot or something wrong.
ive been running around for 20 years with oil pressures that hemi 6 people know are fine, but would make 318 people worry. and my journal size and bearing widths are mostly the same as yours
Dave
i have the joy of 265 6
same pump internals as the 273 318 etc
shifts a lot of oil as flow, never impresses with pressure , does on occasion take a while to show pressure on start, 7 main journals to feed mind.
my sender is electronic the reading on the gauge seems to depend on how much sealer you use, that messes with the earthing
if there is some flow you are unlikley to hang up a bearing at idle regardless of what the gauge says. Your starter is punny in comparison to the forces created by combustion.
next time pump is out check cover for scoreing and clearnce between impellor/clover leaf and cover.
if you spot obvious change at rpm when hot say from 60PSI to 30PSI, when 60 is what you have routinely seen...then worry...its very hot or something wrong.
ive been running around for 20 years with oil pressures that hemi 6 people know are fine, but would make 318 people worry. and my journal size and bearing widths are mostly the same as yours
Dave
ragtopfury
Well-Known Member
Speaking of old stock, how old is too old? Is a 20 yr old still new in the box oil filter too old? Does the filter media break down just from age?
Asking for a friend...... lol
Asking for a friend...... lol
Dave999
Well-Known Member
filter media breaks down when submerged in liquid like acidic suphurised old oil
in theory short of the glue going off due to humidity ( i presume you don't live in a rain forest) NOS should be fine.
it is unlikely that the anti drian back valve would degrade too much, thats the only rubbery bit in there, UV light and heat tends to play a part in rubber degredation. so if its sat on a shelf in its box in a store room or garage it will probably be ok
change a filter and oil on a barn find...that filter has probably broken down.
Dave
in theory short of the glue going off due to humidity ( i presume you don't live in a rain forest) NOS should be fine.
it is unlikely that the anti drian back valve would degrade too much, thats the only rubbery bit in there, UV light and heat tends to play a part in rubber degredation. so if its sat on a shelf in its box in a store room or garage it will probably be ok
change a filter and oil on a barn find...that filter has probably broken down.
Dave
MopaR&D
Nerd Member
Earlier this year I switched from 5W-40 Valvoline synthetic "Euro Spec" to 10W-40 Penn Grade 1 for my Duster. It picked up 5-10 psi hot oil pressure at idle and above. According to the "ratings" it shouldn't have changed.
Dave999
Well-Known Member
yeah the viscosity profile of the oil across the operating temperature of the motor will differ.
i.e 0w30 will be diffferent viscosity than 5w 30 for the same running temperature
the rateing is based on a test at 0*C and i think 100*C (or maybe 99)
i.e 20W50
20 at 0*C 50 at 100*C
what happens inbetween well....who knows you would suspect a move from 20-50
SAE30 we know it is 30 at 100*C we don't know what it is at 0*C could be 40 50 or solidified beef fat...
but with both
at 150*C well we don't know...they don't tell us.
could be 30 could be 40 could be 60 could be 10 could be 5
some oils fall off a cliff when they are way too hot, some don't
more of an issue on an air cooled engine
experience seems to dictate that after a certain temperature is hit the oil starts to lose viscoity....
given that on a cold morning with 20 w50 i have 20-30 psi at idle i must be in the 20-30 SAE range
but after a long run when engine is hot and the oil should be 50 i have 15 PSI at idle??
all i can assume is the hot oil is less viscouse than the 20-30 i ran on when cold but i would expect it to be 50 but it doesn't seem to be that way, you'd need oil temperature gauge to find out what is going on
dunno where i was going with this..just kinda thinking out load
Dave
i.e 0w30 will be diffferent viscosity than 5w 30 for the same running temperature
the rateing is based on a test at 0*C and i think 100*C (or maybe 99)
i.e 20W50
20 at 0*C 50 at 100*C
what happens inbetween well....who knows you would suspect a move from 20-50
SAE30 we know it is 30 at 100*C we don't know what it is at 0*C could be 40 50 or solidified beef fat...
but with both
at 150*C well we don't know...they don't tell us.
could be 30 could be 40 could be 60 could be 10 could be 5
some oils fall off a cliff when they are way too hot, some don't
more of an issue on an air cooled engine
experience seems to dictate that after a certain temperature is hit the oil starts to lose viscoity....
given that on a cold morning with 20 w50 i have 20-30 psi at idle i must be in the 20-30 SAE range
but after a long run when engine is hot and the oil should be 50 i have 15 PSI at idle??
all i can assume is the hot oil is less viscouse than the 20-30 i ran on when cold but i would expect it to be 50 but it doesn't seem to be that way, you'd need oil temperature gauge to find out what is going on
dunno where i was going with this..just kinda thinking out load
Dave
Au contrair. Based on the grade change, one would expect a possible if not likely change in viscosity at operating temperature.
Because in general a 5W-40 and 10W-40 will have viscosity curves that only overlap when the oil is around 212 F.
Then in addition, as Phreakish posted, the grades have an allowable range. Most manufacturers have spec sheets on their websites, and oil nerds will freqently post VOA and UOA viscosities.
The last piece of the puzzle is operating temperture. We can get a ballpark temperature based on coolant temperature - until we start looking at continuous high rpm high load. Oil temperature in the pan is a better indicator of oil temperatures in the engine.
Here's viscosity at termperatures from 32F to 212 F of four "40 weight" engine oils.
Focusing on the temperature range one would expect for normal passenger car use.
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Based on the bearing clearances, Chrysler recommended the following grades in the 1968.
5W-20 was for cold weather only.
SAE 30 was only when outside temperatures were moderate or hot.
You can graph any oil knowing the visiscosity at 40 and 100*C
www.widman.biz
5W-20 was for cold weather only.
SAE 30 was only when outside temperatures were moderate or hot.
You can graph any oil knowing the visiscosity at 40 and 100*C
Graph your oils | Widman International SRL
This is one of my favorite graphs. When it is extended back to 0°C, you can see how the multi-grades thin at a slower rate than the straight grades.
Any engine takes a few seconds. Of your lifters and making noise for the first 10 seconds you could have various causes, bad lifters, bad oil pump, low oil, clogged oil passages or wrong viscosity.
I live in a 70 degree weather average, 10w30 has worked fine for me.
You could try using a lower grade oil than what you have.
People tend to increase viscosity because shows up a higher pressure, but remember that pressure is basically a measurement of restriction.
There are ways to read if you have the right viscosity between comparing oil temperature vs psi. But will take some testing. And trying to test with almost same starting temperature, use rpms and what not. But its something in my opinion worth doing.
Oil pressure should be close to water temperature, not higher though.
If you use a 20w50 yes it will read a higher pressure but will increase in oil temperature compared to a 10w30.
For cold starts its better a less viscosity oil since it will travel faster. Think about it as honey vs maple syrup.
Using a anti drain back oil filter helps for this cold starts. Since oil pump wont need to fill the filters capacity nor it will drain the oil from the top down, or at least reduce the oil coming all the way down to the oil pan.
Yes cranking no start, can create oil pressure, actually it should. Wont be as fast or a high as operating engine though.
So it does help cranking for a few seconds, not mandatory.
I live in a 70 degree weather average, 10w30 has worked fine for me.
You could try using a lower grade oil than what you have.
People tend to increase viscosity because shows up a higher pressure, but remember that pressure is basically a measurement of restriction.
There are ways to read if you have the right viscosity between comparing oil temperature vs psi. But will take some testing. And trying to test with almost same starting temperature, use rpms and what not. But its something in my opinion worth doing.
Oil pressure should be close to water temperature, not higher though.
If you use a 20w50 yes it will read a higher pressure but will increase in oil temperature compared to a 10w30.
For cold starts its better a less viscosity oil since it will travel faster. Think about it as honey vs maple syrup.
Using a anti drain back oil filter helps for this cold starts. Since oil pump wont need to fill the filters capacity nor it will drain the oil from the top down, or at least reduce the oil coming all the way down to the oil pan.
Yes cranking no start, can create oil pressure, actually it should. Wont be as fast or a high as operating engine though.
So it does help cranking for a few seconds, not mandatory.
Most of what people said about oil is correct. SAE XXW is the viscosity measured at -20°C to -35°C depending on the grade. SAE 15@ is measured at -15°C and each lower W grade is 5°C lower in temperature. This is the lowest temperature at which the oil is guaranteed to allow starting and oil flow. Below that is risking oil starvation during a VERY cold start which seldom happens with our cars.
SAE 10W-30 and 10W-40 differ only in how much viscosity modifier (a polymer that thickens the oil only at high temperatures much like STP does). Otherwise they have the same base oil and additives. For older cars, I don't like using SAE XXW-20 as there is so little thin film lubrication with that low of viscosity. The SAE grade (30, 40, 50, etc) is measured at 100°C (212°F) so that is fairly hot.
Personally, I use Chevron Delo 400 SAE 15W-40 in all my older cars as it has the right level of ZnDTP to protect cams. Used it in my 426 Hemi, 383 Cude ('67), and 340 Cuda ('68) and never had any wear issues. For modern engines, I use Costco synthetic 0W and 5W-20 with great success. Due to the volatility of these low viscosity grades, I don't like using them in older cars that are not designed to use such light viscostiy and high volatility base oils.
SAE 10W-30 and 10W-40 differ only in how much viscosity modifier (a polymer that thickens the oil only at high temperatures much like STP does). Otherwise they have the same base oil and additives. For older cars, I don't like using SAE XXW-20 as there is so little thin film lubrication with that low of viscosity. The SAE grade (30, 40, 50, etc) is measured at 100°C (212°F) so that is fairly hot.
Personally, I use Chevron Delo 400 SAE 15W-40 in all my older cars as it has the right level of ZnDTP to protect cams. Used it in my 426 Hemi, 383 Cude ('67), and 340 Cuda ('68) and never had any wear issues. For modern engines, I use Costco synthetic 0W and 5W-20 with great success. Due to the volatility of these low viscosity grades, I don't like using them in older cars that are not designed to use such light viscostiy and high volatility base oils.
Wow, I've really sent you all down the rabbit hole. One of the things I love about this site. Thanks again for all the responses as I never had any idea the composition of motor oil was this complex. I'm assuming that seeing different pressure results across brands at the same oil weight is not out of the question depending on the additive package used in each? I'm really starting to wonder about YY1's comment about the possibility of the oil breaking down even though there's only 1200 miles on it.
And another thing to take into consideration, Mopars do have long pick up tubes. It may take a few seconds longer than a 350 Chevy to pick up the oil. Their pumps pretty much set in the oil pan. LOL
You could send it to one of the companies that does oil analysis (such as Blackstone Labs).
However I don't think the difference oil breaking down would result in such a large viscosity changeat 40 or even 70 * F that the oil volume delivered to be noticibly less.
When oil breaks down the viscosity is still usually within the SAE standard for that grade. Changing grades, for example the difference beween a 10W-40 to a 10W-30, would result in a bigger change in viscosity.
For example, using Havoline Conventional Oil.
At 68 F the 10W-30 had a viscosity around 195 cSt compared with 10W-40 at nearly 287 centiStoke.
Keep in mind that even 195 cSt is still much thicker than viscosity at normal operating temperatures.
Between 180 and 220 F the viscosity is around 8 to 20 centiStoke.
7 cSt is probably getting too thin, so if the engine oil was runnng that hotter than 220, I'd go to the 10W-40.
Another clue to too thin will be a decline in oil pressure at all rpms.
Conversely if the engine tends to be frequently run with oil temps around 180 F, the 10W -30 will flow easier and probably provide higher volume throughout the engine. A clue for too thick is higher pressures at low rpms, but then somewhat flatlining instead of increasing with rpm. That would be the pressure relief opening, or opening further because more volume simply can't be pushed through.
The fact that a little cranking brings the pressure up faster suggests the problem may be the anti-drain back valve in the oil filter isn't sealing, or some other small leakage allowing some of the volume of oil normally trapped in the passages to drain out.
Again my reaction is the same as RRR, 10W-30 may provide better flow resulting in slightly lower idle pressure, but increasing pressure that will continue to match increasing rpm and allow increased volumetric flow at higher rpms. Worth experimenting with. Depending on the valve spring rates, and how hot the engine oil gets, not sure anything is gained with the Hot Rod oil. That's whole other discussion.
If the change in noise and start pressure occured with the change in oil grades, that's probably the answer. If not, then look at oil retained in the system at shutdown.
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MopaR&D
Nerd Member
@Mattax I knew that was the case I was just making the point that oil viscosity isn't as simple as some suggest. Thanks for the graphs that's great info. I was running the 5W back in CO for the sub-freezing (and sometimes sub-zero) cold starts but where I live now that's not much of a concern. It barely gets below freezing here in the coldest parts of the winter, plus I park my Duster in my attached garage.
Dale Davies
Well-Known Member
I would drop the oil pan and plastigage the main and rod brgs. To do the mains you need to hold the crank up so the crank weight does not give a false reading. My method to hold the crank up is to remove the #2 aand #4 main caps and put a short piece of shirt cardboard or cereal box in and just snug the bolts. Then you can check #'s 1, 3, and 5. After that "shim" 1, 3 and 5 to check 2 and 4.
Also remove and check the oil pump clearances. To mark the pump gears to get gear teeth back with their matching teeth, mark with brazing rod sharpened. Works like a pencil but won't easily wash off. Gerotor pumps are hunting so do not matter. End clearance must be checked between the gears and pump housing using a straight edge and feeler gauges.
Cam journal bearings can also be a source of low oil pressure, but the mains and rods would be my first suspects and easier to change. 0.001" undersize bearings can be purchased if Std bearings are on the upper limit of tollerance.
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