I have a 2007 explorer with a 4.0 liter engine with about 182000 miles. At idle( looks like about 550 rpm) the oil light will come on, but the engine sounds normal. as soon as I give it some gas (about 600 to 650 rpm) the light goes out. could it be a bad pressure switch? or maybe the car is idling to low?
The pressure sensor is where I'd turn first. While I'm not big on Remove and Replace (R&R) mechanics, this is a cheap option. The other thing you can do is to remove the pressure sensor and put a mechanical gauge in its place, just to see if the electronic one is accurate. Oil pressure lights come on around 5psi (or thereabouts, depending on the manufacturer's design). What you are describing sounds exactly like you have low oil pressure, though.
You could try changing your oil to a heavier weight. If you are running 5w-30, you might try running 10w-40 and see if the light no longer comes on. If it doesn't come on, you'd most likely do have low oil pressure.
Realistically, your oil pressure could actually be that low and the engine still not make noise, but a defective oil pressure sensor could also be at issue. Changing it would not be out of order.
Just to add to @Paulster2 answer Perhaps the oil pressure switch is correct - the oil pump will certainly be worn... perhaps a new pump or even just the gears may help... Some cars had an ignition cutoff if the oil pressure was not sufficient - that was by-passed or the pressure improved...
I have had a couple of high mileage used cars that had low oil,pressure because the screen on the oil pump suction was partially blocked by sludge. I removed the screens and that was an improvement. And , the bearings may have more clearance because of wear; as noted a heavier oil viscosity would help with this condition.