Oil Pressure

Ford 860 gasser. I re-built the 172 engine. 156 hours on rebuild. Oil pressure stayed between 43-48 psi. Just completed the fourth oil change with new filter, same weight oil and same brand/model filter (Fram).

Only thing I did different this time was add Sea Foam to the oil in the appropriate ratio.

Now oil pressure reads...
50 lbs. @ 540 rpms
40 lbs. @ 1000 rpms
60 lbs. @ 1100 to 1400 rpms
then drops back to 40 lbs. @ 1500 rpms.

I'm guessing a restriction somewhere and has nothing to do with the added Sea-foam. Which only leaves the oil filter in the equation. Can you get bad oil filters?

Should I replace the oil filter or continue to use it?

IMHO ditch the Fram filter. I have seen oil presure issue with them on several occasions.

If it was mine I'd start by ditching the sea foam... then I'd ditch the Fram filter. My preference is FleetGuard filters but Wix or even Baldwin will do. Donaldson is also a very good filter. Second thing... I'd make a point of using a DIESEL RATED, heavy duty engine oil in either 10W30 or 15W40 grades depending on your present ambient temperature range. That alone should build oil pressure and a good HD oil will have sufficient detergents to keep the engine clean.
You may have a combination of a bad filter or just a blocked filter after the seafoam has loosened a bunch of crap up........ but really 55-60 is where the pressure should be on a tight bottom end of a 172 engine.

Rod

Got to relate a story about the Fram filter.Back years ago when the kids were in highscool, I had several Ford Escorts. One of the girls Got an Escort too hat.Cracked head. Normal. So we were over hauling the engine, pulled the crank and the rear main bering was starving of oil. The oil hole in the block had a "plastic plug" in it. Finally cut the oil filter apart and found the plastic releaf vqlve was no longer in the filter. It had gotten hot enough to disform. Needless to say I have never used a Fram filter since. Buy the way, the motorcraft FL-400 filter has a metal relef valve.

Just another thought if the oil and filter doesn't do it.
You may have loosened some crud and restricted the gauge line,
or its possible the gauge went bad.
I've had a few bad gauges lately, so I may be a little gun shy.

On Fram filters, I use the mid priced filter, forget what you call it but it has the silicon seal and the black friction bottom so you can easily install/remove it and it's the one with 6x the filtration of bargain units. I also have Delco and WIX, all in 3 diesel tractors, my new Chevy truck and lawn mowers.

I spent considerable time on the www comparing construction, filtering capacity (how small a particle do they trap), rated flow, and pop off valve release pressure. I then made up a matrix of filters for all my stuff so that when I went to the bin and wanted a filter for xyz machine, I knew which one I was looking for.

In the process of doing that, I cut open used filters of the three brands and inspected the construction and integrity of the filtering capability after having been in use for a year at least on all filters and that's where I was able to see the differences in construction techniques.

In all honesty to all 3 mfgrs. I couldn't find any difference in the filters with respect to integrity. Even though the Fram is put together with paper where others use metal, the paper was intact, the glued joints were still intact and strong and everything else was still very servicable.

So, I am confident that any will serve my purpose.

HTH,
Mark

Oh, forgot the main event. I too think crud got dislodged causing the variance. My Ford diesels have varying oil pressure from about 40 at idle to 55ish at WOT, and have for years. I use WW brand or Shell 15w-40 and no additives in the oil.

Mark

Oh, forgot the main event. I too think crud got dislodged causing the variance. My Ford diesels have varying oil pressure from about 40 at idle to 55ish at WOT, and have for years. I use WW brand or Shell 15w-40 and no additives in the oil.

Mark

There may be a grade of Fram that is good, but the results of a test of many filters that comes up here from time to time shows Fram at the bottom. What is Walmart's choice? Why take the chance? There are too many highly rated filters.