Ok, so I just finished my engine swap in a 1998 Buick LeSabre. Donor ended up being a 2004+ Impala. Best I could tell was that the Plenum was stamped Feb 02, 2004. So, the install went great with some suggestions from this forum and others....a big thanks to those who assisted!
Now the question:
Once my LeSabre warms up, I'll notice a drop in oil pressure when I slow down or come to a stop (ie - getting off the interstate or at a stop light). I'll stick right at 40psi when I'm running, but then drop down to the red when I'm stopped. Just a few things I've observed
1) Only happens when the engine is warm
2) Previous engine called for 10W-30 but donor calls for 5W-30. Only had 10W-30 on hand for the oil change
3) 1qt of the oil change is Marvel Mystery Oil. Supposed to help clean the engine, but the consistency is more like Water
4) Reused the Oil Pressure Switch. Was working fine before. Only a couple months old, so I pulled it before I yanked the engine, then reinstalled after the new engine was set.