8.1 Oil Pressure and Filter

[BurbMan]

Last oil change I installed a Fram Ultra Guard since the Wal-Mart by me stopped carrying AC Delco filters. Local auto parts stores don't seem to carry the AC Delco filters either. Right after that I ordered some OEM PF-454 filters from Rock Auto so now I have a few on hand.

On a road trip to Chicago last week I noticed that the oil pressure was lower than normal....it was only running about 20 psi at idle and about 45 psi at 2500 RPM. I did an oil change yesterday with a little over 5k miles on the oil, and today I see the oil pressure is running about 10 psi higher, 30 psi at idle at about 55 psi at 2500 RPM with the AC Delco filter installed. This is where the oil pressure always was on this truck, so I consider this to be normal, so the oil pressure was running about 10 psi lower overall with the Fram filter.

The oil I am using is Mobil-1 5W30 Hi-Mileage formula.

I'm not sure if this is a function of having 5k miles on the filter or if the Fram filter is too restrictive vs. OEM. I never recall seeing a drop in oil pressure over the life of an oil filter. Does that mean the Fram is filtering better?

As an aside, I changed to synthetic at about 100k miles (160k on the truck now) and have noticed about 1 mpg improvement and I no longer get the infamous "piston slap" at startup...much quieter now. For the first 100k miles, I used regular dino oil with a 3k change interval, now I go 5k with synthetic.

Who makes the best oil filter these days anyway? The AC Delco's online were only $3.40 each, the Fram was $8+ at wally world, and I see they now have Bosch filters at $10+. Tempting to think that the more expensive filter is better, but as with anything else, that's more often marketing than actual quality.

I also did another Blackstone sample, and will post results when it comes back.

[AH64ID]

I am not aware of any OEM oil pressure senders before the pump, they are always (IME) post filter.

The oil goes from the pan, thru the pump, into the filter (bypass is here, some filters/engines are internal and some are external to the filter), then to the main galleys. The pressure sender/switch is in one of the main galleys.

There are probably some engines with it pre-filter, but none that I have seen.

[BurbMan]

Byronlj, that's interesting and hadn't thought of it that way...so the sending unit is actually measuring back pressure at the filter? Low a less restrictive filter produces a lower gauge reading....hmmm....would make sense.

Ben, that's funny! When they first started emissions checks in NY years ago, we used to do the same thing....run the tank almost empty and put in 3 or 4 cans of STP Dry Gas, the engine was practically running on alcohol and burning clean! Here in KY, they repealed the safety inspection requirement, forget about emissions....

Geotex, you got me...I know the old Sub forum is all but dead. I can think of a few names but none from NJ, that's what's throwing me...but you're a fellow L18 owner!

[byronlj]

I believe your oil pressure sending unit is located before your oil filter. If so, you have lower pressure with the Fram filter because it is less restrictive, not more.
I got the wrong filter on a car we were servicing and the filter blew up. The oil pressure gauge was pegged just as it blew. So, yes, a filter can change your pressure.
Dave

[BenK]

ON my way to fill it up after Calif SMOG check.

Purposely run it down low and add two bottles of HEET (yellow) and ace the test
even lower than without the HEET. Lower than most cars without the HEET but like
to get it lower yet because Calif labels all my vehicles 'high emitter profile'
whatever that means...all of my vehicles have passed way below...except
for the Silverado failed with the previous engine (dieing and leaky
intake manifold getting engine oil into the chambers)

smogtest


geotex1 ...guessing either had dinner with you at that brewery
the last time you were out west...or you had the speed boat

[BurbMan]

I don't know about "running hard"...I was cruising at 75 mph without the trailer, RPM about 2300 or so. It's 5.5 hrs each way to Chicago, about 335 miles. The 8.1 has used 1 qt about every 3000 miles since new. Seems like consumption has dropped a little since going to synthetic. The nice think about the 3k oil change intervals was that when it was a quart low it was time to dump the oil. Now that I am running longer intervals, I have to add some. A handful of times I have had the "low oil level" message come on, which will trigger when it's 2 qts low. Seems to use more if too much time around town and too few hiway miles.

Even though pressure was down I never got a "low oil pressure" message so even though pressure was down flow must have still been adequate to keep the engine lubed.

I am far from an expert on this stuff, so just putting this out there for discussion...I'll be sticking with the AC Delco filters from here on out.

Ben, you shouldn't let your fuel level get so low, it's not good for the fuel pump!

[geotex1]

BurbMan wrote:
From a practical standpoint, what's the impact on engine wear from a 22 micron particle vs. a 20 micron particle?

Practically speaking, absolutely none. Your engine sees much more wear every day from initial start up than such tiny delta in particle filtration. FRAM, once upon a time, wasn't a bad filter. However, I won't use them if you give me them for free! I bet the interval at which you change your oil that you aren't even reaching substantial breakdown, especially if you are checking with lab analyses...

Given your handle as well, you and Ben would both recognize me from the old PacAudio GM forum and well as the Sub-Yuk forum if I was using that username here! :B Clues are that I'm an old engineer and a long-proven gearhead with the two intermingled...

Stick with the Delco filter on the BB. Can't beat them all-around when purchased by the case! In addition to my old L31, I also had an L29 and have L18. 😛

[BenK]

Oh, before someone says an anomaly...here is my 1980 Silverado's dash oil gauge
(direct, no sensor)

Built engine (CAM, flowed/ported/matched/polished, CC'd, SS valves, etc) 5.7L
four bolt main. Automatic. Mobil 1 5-30W at 500 mile first oil change
only NAPA Gold

At temp and on the highway (have a 160* stat) and pegged
Silveradodash

At temp and idle. Cold will be high side of 60PSI, but not pegged
Silveradodash oilgauge

[BenK]

May not be the Fram filter...did you run your 8.1L very hard before
you noticed the reduced PSI?

I've changed out a charge of Mobil 1 5-30W & PureOne filter after about 500 miles

My 7.4L at +163K miles does not consume oil. Never did...but one time after a
very hard run up to Lake Tahoe with the gang...

On the way back...noticed that my oil PSI was fluctuating and at home down a quart

Knew the oil was beat up and changed both oil and filter. PSI was back to normal
at startup. This was back at around 100K miles



At idle and up to temp (have a 180* stat with a 1/32" dia hole drilled in the flange)
It is now just a hair below 40 at +163K miles
mydashatidle mydash



At about 2200 RPM up to temp. Now around 170PSI at +163K miles
mydash mydashatspeed

[AH64ID]

BurbMan wrote:
Good info and thanks. What's your opinion on the pressure drop using the Fram?

I have never been a Fram fan, but that still shouldn't have dropped that much.

There is a chance there is less dirt holding capacity in the Fram, and it was just at the end of it's service life.

What I find odd is that it was 10 psi off at both rpms, I would have thought a clogging filter would cause a greater pressure drop as flow increased. Maybe the bypass was cracking???

[BurbMan]

Good info and thanks. What's your opinion on the pressure drop using the Fram?

[AH64ID]

carringb wrote:
Wix is good. Napa Gold = Wix

I had pressure problems with the Purolator PureOne filters. It was restrictive enough when cold it would cause the bypass valve to open, causing my pressure gauge to go to zero.

That's why I like the Amsoil filters, better filtration and the media also flows better so there isn't a restriction.

BurbMan wrote:
What I was thinking....there has to a balance between filtration and flow. From a practical standpoint, what's the impact on engine wear from a 22 micron particle vs. a 20 micron particle?

Is it better to capture 95% of the particles larger than 20 microns (Wix) or is it better to capture 99% of the particles bigger than 22 microns (Delco)? Any filtration engineers out there?

20 vs 22 is minimal in terms of wear difference, and both are good for full flow. I would also bet that the Wix is getting close to 99% by the time you get to 22µ anyhow.

[BurbMan]

What I was thinking....there has to a balance between filtration and flow. From a practical standpoint, what's the impact on engine wear from a 22 micron particle vs. a 20 micron particle?

Is it better to capture 95% of the particles larger than 20 microns (Wix) or is it better to capture 99% of the particles bigger than 22 microns (Delco)? Any filtration engineers out there?

[carringb]

Wix is good. Napa Gold = Wix

I had pressure problems with the Purolator PureOne filters. It was restrictive enough when cold it would cause the bypass valve to open, causing my pressure gauge to go to zero.

[AH64ID]

BurbMan wrote:

AH64ID wrote:
Amsoil filters are among the best at 20µ at 98.7%,
Wix is also good at 20µ at 95%.
Donaldson is 22µ at 98.7%.
PureOne are hard to beat. 20µ at 99.9% (Amsoil used to have this same rating, but it changed in 2011.. not sure if there was a standard change??)
AC Delco PF454 22µ at 99%.

Can you help me understand what these numbers mean? Is that largest micron particle size and efficiency?

Yes, for example the Amsoil removed 98.7% of all particles 20µ and larger.

[weathershak]

BurbMan wrote:

weathershak wrote:
I use the PF1218 1 qt filter or a WIX alternate .

The oversized filter won't fit in a 4WD application because of the front drive shaft and transfer case...

oops, I learned something.