2014 gmc low oil pressure when hot

[kamaroman]

I purchased a 2014 gmc 5.3 with 80k. the lifters were all replaced under warranty. soon after i noticed 10 psi oil pressure after driving 25 min on highway. dealer replaced oil pump still has 10 psi after 25 min of driving. when i first start up its at 40, oil pressure goes to 70 when rpm exceeds 3500 rpm. oil pressure starts to drop to 20 after 10 min and seems fine. after 25 min it drops to 10 on guage. i had oil pressure checked with mechanical guage and confermed guage is accurate. i asked dealer to che k the screen under oil pressure switch they said it was clean. at this time dealer says nothing is wrong due to specs at 1000,2000,3000 rpm. i called gm customer care and they said to get different dealer to look at. i did and they confermed rpm at different rpm and charged me 118.00 gm customer care did nothing to help me out. i have never seen any truck with 10 psi at idle. does anyone else seem to have this issue?