Any oil pressure at all indicates an oil pump is producing more oil volume than an engine needs. If a bearing gets one drop of oil from the pump every time a drop falls back into the sump, the bearing will get lubricated properly, and the pressure will be zero. The trick would be getting exactly the right amount of oil to every place in the engine that needs lubrication.
Your cruise pressure looks about right. Anything more would just rob unnecessary horsepower from the engine to drive the oil pump. The low pressure at idle indicates you've got a bit more bearing clearance than normal- - - -replacing rod bearing, and possibly main bearings should bring the idle pressure back up if it bothers you. Unless the hydraulic lifters start rattling at idle, I'd probably just ignore the idle pressure, however. Idiot lights turn on at about 5-7 PSI, so a lot of people who don't run a pressure gauge probably don't realize how low their oil pressure actually is.
Jerry
