Case study 1994 Grand Cherokee, 271,XXX Kms on the odometer, 4.0L auto.
Scenario oil was changed 2 days ago.
Day one: on start up idle is rough like timing is retarded. Next lifer/rocker tick is evident.
Day two: oil pressure is 2-3 bars low at idle and at 3,000rpm not reading at even the half way point on the OEM gauge. Idle and lifter/rocker tick is worse.
So I decided to pull the "partsmaster" filter as it all began after the oil change,.. It was VERY hot to the touch that had me thinking,..
With the stock pile of Jeeps I have at the house I have some good quality filters always in stock.
So when I removed the filter I compared it to a quality Baldwin filter.
I replaced the "partsmaster" filter with the Baldwin, replaced the lost oil and ran the same tests. The Jeep responded very positively and idle oil pressure is higher than 3,000 rpm pressue with the old filter. We have regained previous oil pressure before the change , noise and odd idle seem to be corrected for now.