So here is my experment,

changed fluids and filters bolth times, before measuring oil PSI with a mechanical PSI gauge, I was driving on the freeway for at least 30 Miles, all temps were up to regular opperating tempatures. It was 70 Degs today

Ok the first row is RPM
the second row is synth rotella t 5W-40 PSI
the third row is synth Amsoil 15W-40 PSI
the fourth row is outside air temp

750 17 28 70
1000 20 35 70
1250 22 41 70
1500 25 48 71
1750 29 51 71
2000 33 58 71
2250 36 58 71
2250 37 58 72
2500 37 59 72
2750 38 59 72
3000 39 59 72

As you can see 59 it the highest oil PSI I got, I think the oil bypass is set at or near 60 or so.

So my question is 1) what are thoes PSI numbers gona look like when its 115 Degs in summer, and 2) Why if bolth top numbers of the oil say 40, shouldnt the psi be nearly the same at 1500 RPM ?, I understand the lower numbers being differnt at idle?

thanks for your input

Rick

40 is the weight of the oil,not the psi it will produce.

Remember;

Lubrication is flow not pressure.

40 is the weight of the oil,not the psi it will produce.

Remember;

Lubrication is flow not pressure.
Right, what I meant to say is if bolth of the top numbers are 40 ( 10w-40 and 5w-40 ) bolth oils should behave the same at full hot opperating temp, the only differance should be at start up and when its real real cold out side.

Thanks for bringing my attention to that

Rick

5W50 will be a lighter 5 weight (thinner) when cold, and get to 50 weight (thicker) when hot. The 15W40 will start out a little thicker at the start when colder, and top out at 40weight when warm. The higher the last number, the better it is when the ambient temps are higher. Our durmax manuals state to use 15W40, but 5W40 is better to use in colder ambient temps. It makes starting in the colder climates easier and provides better lubrication for the motor.

Sory I F'ed up the title

It should read 5w-40 and 15w-40

I think thats an interesting observation, it seems that oil psi would be the same between the two...

How did you get the same outside air temp with both oil changes to match each other??

I have a question: is our oil pump putting out a constant volume/rpm? Then isn't pressure a response to resistance to flow for a constant volume?

Thinking out loud, So the pressure sensor detects pressure after the pump and the oil that flows better will read higher pressure? In this case the Amsoil?

Or do I have it backwards?

Right, what I meant to say is if bolth of the top numbers are 40 ( 10w-40 and 5w-40 ) bolth oils should behave the same at full hot opperating temp, the only differance should be at start up and when its real real cold out side.

Thanks for bringing my attention to that

Rick


I wasn't sure where you were going Rick,pardon me for making you look bad..:cool:

I have a question: is our oil pump putting out a constant volume/rpm? Then isn't pressure a response to resistance to flow for a constant volume?

Thinking out loud, So the pressure sensor detects pressure after the pump and the oil that flows better will read higher pressure? In this case the Amsoil?

Or do I have it backwards?

to answer your first question, volume/rpm, I THINK it has to do with visocity, the thicker the oil is, the less volume you will get, but higher psi.

and the thiner something is the more flow you will have and less PSI
also if this helps any, I THINK oil PSI is what is called "residual PSI"
anotherwords, the pressiure left over while the oil is being forced out thru all of the bearings and lifters etc.

AGAIN, I THINK THIS IS THE WAY IT IS.

second question, flows better/higher PSI, I dont know for sure but I do know that thincker oil will show a much higher pressiure on the oil pressiure gauge, espically when its hot

One thing I'm tring to understand is, what is better, flow or PSI ?
if flow is better for the motor it would seem to me the a thinner oil would flow more volume, theirfore lower PSI.
and if PSI is better, then a thicker oil and higher PSI and lower flow levels, would be good

I wasn't sure where you were going Rick,pardon me for making you look bad..:cool:

I didnt take it that way
Thanks anyways

Im just trien to figure this stuff out

I think thats an interesting observation, it seems that oil psi would be the same between the two...

How did you get the same outside air temp with both oil changes to match each other??

bolth tests were done about 15 miniuts appart

to answer your first question, volume/rpm, I THINK it has to do with visocity, the thicker the oil is, the less volume you will get, but higher psi.

and the thiner something is the more flow you will have and less PSI
also if this helps any, I THINK oil PSI is what is called "residual PSI"
anotherwords, the pressiure left over while the oil is being forced out thru all of the bearings and lifters etc.

AGAIN, I THINK THIS IS THE WAY IT IS.

second question, flows better/higher PSI, I dont know for sure but I do know that thincker oil will show a much higher pressiure on the oil pressiure gauge, espically when its hot

One thing I'm tring to understand is, what is better, flow or PSI ?
if flow is better for the motor it would seem to me the a thinner oil would flow more volume, theirfore lower PSI.
and if PSI is better, then a thicker oil and higher PSI and lower flow levels, would be good



I would think flow would be more desireable than pressure. I would rather have more oil running over/through a bearing than less oil with more pressure behind it.

Alright, even though they are supposed to both protect like a 40-weight at operating temperature they obviously are somewhat different since they show different PSI, no? If the 5w-40 flows that much easier through the motor, its got to flow that much easier away from bearings and rings also right?:think:
Lookin' at that kinda makes me think I should go back with a 15-40.
BTW it never gets down to 0 or even 10F here so I know the 5-40 isn't needed, I just thought it was better protection.:confused:

I think the better question is what is the viscosity?

While the Pressure and Flow are important parameters, but it depends on a lot of variable ambient and the way the car is run. The higher the temp. the more difficult for an oil to maintain its viscosity. If the oil cannot maintained the viscosity, then it is a bad oil.

The question are:
Is the temperature ambient or engine?
What is the relationship between viscosity and temperature and pressure?

A more definitive test would be an oil analysis because that will determined if certain oil is better for your engine than others in terms of wear. This is also depends on each engine. The same Dmax engine on different trucks means different engine. Also an engine operating at LA may not be behaving the same as in CT.

Anyway, that is my thought. Some of the oil expert from BITOG who also hang out here can probably give us some enlightenment.

Alright, even though they are supposed to both protect like a 40-weight at operating temperature they obviously are somewhat different since they show different PSI, no? If the 5w-40 flows that much easier through the motor, its got to flow that much easier away from bearings and rings also right?:think:
Lookin' at that kinda makes me think I should go back with a 15-40.
BTW it never gets down to 0 or even 10F here so I know the 5-40 isn't needed, I just thought it was better protection.:confused:

Now you can understand what I'm talking about, I think the same way, but at the other end.
your thinking about the cold side, 5W-40 vs 15W-40.
I'm thinking about the high side.
In the summer time it never gets below 100 degs. F here in southern AZ where I live.

Im thinking of tring to find mabee a 20W-50 or a 30W-50.
like I said I dont need a cold weather protection of 5W or 15W.
In my chevy cars, trucks and boats I run straight 40W, If I put 10W-30 in gas truck, when hot I will start to hear lifter noise at idle.

I was told the higher oil pressiure is better than low !

Now you can understand what I'm talking about,

I was told the higher oil pressiure is better than low !



Put in straight 60 wt then!!!! Lubrication = Flow not pressure.

What would get to your bearings faster and more often water (5w40) or jello (20w50)????? A little analogy to simplify my point.

It is important to maintain a sufficient pressure as well as flow. The oil should be thin enough to go between the bearing. yet should be thick enough to maintain between the bearing and create a barrier.

5W50 will be a lighter 5 weight (thinner) when cold, and get to 50 weight (thicker) when hot.

Just a nit (sorry) - I know what is (correctly) meant here, but think it's important to make sure that everyone understands the multi-vis oil behavior.

Using the 5W/50 example, the oil behaves like a cold 5W straight grade when cold, and behaves like a HOT #50 straight grade when hot. A straight 50 weight oil when hot is still thicker (more viscous) than a straight 40 weight when hot, but either are still thinner (less viscous) than they would be cold.

A lot of folks think that the oil magically turns into something the thickness of corn syrup when hot, which it, of course, doesn't. Just look at hot oil draining out of the crankcase.

I am a little worried with the listed oil pressure number. To me it indicates that the oil can not maintain enough pressure to provide good lubrication/barrier between the bearings.

I'm more interested if the temperature is oil temperature, not outside temp.

I am a little worried with the listed oil pressure number. To me it indicates that the oil can not maintain enough pressure to provide good lubrication/barrier between the bearings.

I'm more interested if the temperature is oil temperature, not outside temp.

the temps are ambient out side air temps.
temps when read with a digital temp gun at the side of the oil pan are 300+
I didnt preform at oil temp reading on this experiment.

I think thats an interesting observation, it seems that oil psi would be the same between the two...

How did you get the same outside air temp with both oil changes to match each other??

both tests were done about 15 minutes apart

So does old oil vs. new oil figure into the discussion? In a controlled experiment, you would want to measure each oil at the same point in it's life cycle I would think...