Changed the oil & filter in my 6.2 pickup yesterday,went with SAE 30 from Walmart in the 2 gallon jug ($17.99) ...first time I've put SAE 30 in it..this stuff is SN-CF rated,which is adequate for an older diesel like mine..
I put a AC PF1218 oil filter on it,I had several hanging around ,I had bought at least half a dozen when a local department/home/auto store chain closed up last year,they had Champ & AC oil filters for $1.99 on clearance..also bought 2 cases of SAE 30 Wolf Head oil for $24 a case ,that is also SN/CF rated..I use that in my air cooled small engines..
The engine had a Champ filter on it before,and the oil pressure was bewteen 30-45 lbs cruising along past idle,with 15W-40..at idle it was between 15-25 psi..the gauge needle flutters around at certain rpms,its always done that,probably the sending unit..
Now its barely going over 30 psi at any speed..
I also added about 3/4 of a quart of Marvel "Heavy Duty Oil Stabilizer" I had,that is much like Lucas oil stabilizer,only it is red and smells just like Marvel Mystery Oil..it is thick gooey stuff like STP,etc..
I was expecting the oil pressure to go up with SAE 30,not a bit lower..
Especially with the stabilizer stuff added
..only thing I can think of is maybe the AC oil filter has more resistance to flow that the Champ one,and it reduces the oil pressure some..

..maybe the pressure will go up after some miles,I've had other engines show lower pressure after changing the oil for awhile ,then it increases some later on..like the fresh oil thickens up after some miles..
The engine seems much quieter at idle than before,but at a fast idle or cruising it still is a clatter-mobile..
I also added about 1/2 a quart of SAE 30 to the fuel tank,I think that made more difference than anything.!.put 55 miles on it earlier this morning on back roads cruising to and back from the flea market..
One thing puzzled me--I drained all the oil oil out and was able to put it in a 5 quart jug without overflowing--the engine is supposed to hold 7 quarts..the filter might hold a pint,and the oil level was about 3/4 of a quart low when I drained it,so I should have got 6 quarts out..
I put in roughly 5 quarts of the new oil--it is hard to judge just how much you put in ,the jug has no clear measuring level indicator,so you have to guess...I put in over half of the 2 gallon jug-- and the dipstick read full,then I fired it up and let it run a few minutes,shut it off,checked it again,now it was almost a quart low,so I topped it off to the full mark--I think there is only 6 quarts in it though,I even took the dipstick out of my 85 Burb's 6.2 and checked it with that one,it reads the same...now I'm wondering if I've been running it a quart or two "low" or not ever since I've owned this truck....
Next oil change I'll buy single quarts and put 7 in with a filter,and see how high it reads on the dipstick..if its over the full mark and doesn't act "overfilled",I will file a new full mark on the stick..if it hasn't chucked a rod or snapped the crank by then,that is !..
Next on the list of things to do is change the gear oil in both diffs,it is probably the original lube from 1982..I've kept them topped off,but I know they must be nasty by now...I've only kept the transfer case topped up too,never changed it--I have put maybe 15,000 miles on the truck since I got in in 2003 and it did sit a lot..the TH400 I'm sure would like a new filter & fluid too,its seen a lot of plowing abuse..