I've got a 2001 LB7 with 278K miles. I'm starting to see the oil pressure gauge in the IPC "wandering" a bit at idle. At driving speeds, the gauge appears to be steady throughout the rpm range. When I'm idling (park, stopped in traffic, etc), the gauge is not always steady and drifts +/- 1 mark (max). I've been running Rotella 5W-40 T6 for years without problem and changed it (and filter) about 1,000 ago. Any possibility that the oil pump is showing it's age and possibly on its way out? (If so, how much of a PITA is it to change out?) Could it be the IPC itself?