Changed oil (Castrol 20W50) and filter (Bosch).
When engine is hot (90C-100C) pressure is now between 0.5 to 1.0 with car in gear, and 1.5 with car in neutral. With engine at approx 83C, pressure is 2.2 in gear and 2.5 in neutral.
The old oil I removed ran very freely and quickly. I suspect it was a lighter, winter weight since it was last changed in March (car was not driven much since then). I also am wondering if lighter oils keep the engine generally cleaner, and if my 20W50 is too heavy....
To be safe, I will have the sender checked this Friday, and perhaps have the service shop change the oil yet again to whatever their standard is, since they have maintained the car in great condition for the past 7 or 8 years. I can live with the low pressure indication if I know there is not a problem.