Oil pressure sending unit question.

[muddy12]

Where in the system does the sending unit read the pressure?
In other words, does the sending unit read the pressure before the filter, or after the filter?

Wasn't able to get my normal brand of oil filter when I changed the oil yesterday, and now my pressure is running a couple PSI higher than normal.

If the sensor is located "pre-filter", then the increased pressure, to me, would mean that this new filter is more restrictive than my normal one, and should be avoided in the future.
If the sensor is located "post-filter", that would lead me to believe that the new one is less restrictive, and maybe I should continue using the new brand.

thoughts?

 

[chris52010trx4]

oil pressure sensor is above filter

 

[muddy12]

oil pressure sensor is above filter

I know where it is physically located on the engine.

I guess a better way to ask my question would be; Does the sensor read the pressure GOING INTO the filter, or the pressure COMING OUT of the oil filter?

The increase in pressure that I am experiencing from the different brand of filter could be either a good thing or a bad thing, and it depends on which side of the filter (inlet or outlet) that the oil pressure is read from.

Pressure is made when there is a "resistance to flow". If the oil pressure is read on the inlet side of the filter, an increase in pressure would mean the new filter is more restrictive and I'm now getting less flow on the outlet side. If the pressure is read on the outlet side, the increase in pressure means that the new filter is less restrictive and I now have better flow past the filter/to the rest of the engine.

EDIT: Think of it like this,

oil in pan ---> pump ---> filter ---> lubing engine parts ---> back to pan.
Does the oil pressure sensor read the pressure before the filter or after?

 

[muddy12]

No body knows??


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[turkeybird56]

Honestly, never worried about it. But I have a MY 19, and the PSI is not a real pressure, but a computer algorithm...

Haven't had a real gauge in any vehicle I have owned since my 67 Impala SS, with a set of the old triple gauges that had plastic lines running all over the place under the hood, Just saying.....

 

[Wild one]

You might have to find a oil flow chart .I think it reads pressure after the filter,but not entirely sure.Dig around some,there's gotta be a flow chart somewhere for the 3rd Gen Hemi engine

 

[muddy12]

It wouldn’t concern me so much, but I’m seeing an 8 to 10psi increase across the board, and the only difference is the brand of filter I used this time.

I’m either going to start using this filter all the time, or switch back to the old brand. Which way I go depends on where the pressure is read.

I haven’t had any luck finding an oil flow diagram for the 4th gen 5.7’s yet, but I’ll keep digging.


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[Wild one]

It wouldn’t concern me so much, but I’m seeing an 8 to 10psi increase across the board, and the only difference is the brand of filter I used this time.

I’m either going to start using this filter all the time, or switch back to the old brand. Which way I go depends on where the pressure is read.

I haven’t had any luck finding an oil flow diagram for the 4th gen 5.7’s yet, but I’ll keep digging.


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Post up the filter that's giving you the higher reading.There's guys on here who can tell you whether it's a good or not so good filter. There could be a downside to higher pressure after the filter,and that could be that it's not filtering as well,and is letting more particles through. I'm pretty sure the sender is after the filter,as that's where the turbo guys are tying in to get filtered oil for the turbo,but like I said,i'd see if there's a flow chart somewhere.Somebody with an Alldata membership might be able to find it on Alldata.

 

[muddy12]

Previous filter was mopar.
The current one, that’s giving the higher pressure is a Mobil 1.


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[muddy12]

Honestly, never worried about it. But I have a MY 19, and the PSI is not a real pressure, but a computer algorithm........

Even so, I still feel like a ~10psi increase in the pressure (even if it's algorithm generated) is worth looking into.

I have always used the MO-899 filters and Valvoline synthetic blend 5w20 in this truck since purchase. This time around, when I bought oil and filter, they were out of the 899's, so I went with a Mobil-1 M1-210 filter.

From digging around here a bit, it seems the general consensus is that the M1-210 is a good filter. I'd still like to figure out why I getting higher pressures though.
Still no luck finding an oil flow diagram.

 

[Scottly]

Pressure is read post filter, for a reason. If it was read pre-filter, you could clog a filter and never know it. And know that flow is more critical than pressure. Pressure keeps bearing surfaces apart, but flow keeps those surfaces cool. As for filters changing pressures, keep in mind that some filters have more media than others, and some have media that restricts smaller particulates. Bottom line: Your truck is designed to run on a certain type/construction of oil filter.

 

[Scottly]

Here's some good ********* reading on the subject: http://www.austincc.edu/wkibbe/oilfilterstudy.htm

 

[muddy12]

Pressure is read post filter, for a reason. If it was read pre-filter, you could clog a filter and never know it. And know that flow is more critical than pressure. Pressure keeps bearing surfaces apart, but flow keeps those surfaces cool. As for filters changing pressures, keep in mind that some filters have more media than others, and some have media that restricts smaller particulates. Bottom line: Your truck is designed to run on a certain type/construction of oil filter.

Here's some good ********* reading on the subject: http://www.austincc.edu/wkibbe/oilfilterstudy.htm

Scotty,
thanks for the response and post filter conformation. I was assuming that the pressure was read "post filter", but you know what they say about making assumptions. LOL
Also, thanks for the link to the info about the filters, lengthy but a good read.


So, a follow up question to anyone that stuck around this long;
Would you be concerned with this situation?
With the Mopar MO-899, my warm pressures were high 20's at idle, and mid 40's cruising.
With the Mobil 1 M!-210, my warm pressure is mid to high 30's at idle, and mid 50's cruising

 

[Scottly]

With the Mopar MO-899, my warm pressures were high 20's at idle, and mid 40's cruising.
With the Mobil 1 M!-210, my warm pressure is mid to high 30's at idle, and mid 50's cruising

Same oil weight, type, and brand, measured when zero miles have been accrued on the oil?

 

[muddy12]

Same oil weight, type, and brand, measured when zero miles have been accrued on the oil?

Yes, everything exactly the same. The only difference was the filter.
The end of my oil change routine is as follows;
1:check oil level on dip stick.
2:start engine & check for leaks.
3:shut off engine
4:re check oil level on dip stick.
5:go for a drive to get everything up to temperature.
The change in pressures was noted during this "post oil change" drive.

Although, as I'm thinking about it now; With the mopar filter, I never noticed much (if any) of a change in pressure between fresh oil, and 5,000 mile old oil. I'm beginning to think that the mopar filters are just more restrictive.

Every thing I've found so far points to the Mobil 1 filter being a good quality filter, and an acceptable alternative to the factory filter, so I'm not going to worry about it too much. It will be interesting though, after a few thousand miles, to see if the pressure comes down any. Maybe a dirty Mobil 1 filter will show the same "post filter" PSI as a clean Mopar filter?

 

[Scottly]

My $.02...As long as the pressure is within factory spec, so be it...