I have an 06 MCS with some oil pressure issues. It shows 133K.
It all started with an oil light at idle. Oil not low, but awfully dark. Since it's a recent purchase, I reviewed the original owner's maintenance records the oil was but 3000 miles old.
Had the oil changed to Mobil1 5w30 and replaced the timing chain tensioner. Back to silence, but oil lamp still lights at idle after about 10 to miles of driving.
After some research I had the Wix filter replaced by a Mann filter as suggested by MiniMania. No change in behavior and accumulated about 400 miles. Oil is dark once again.
Decided to change to 15w50 Mobil1 .
Voila! No light .... for a couple days. Then back to flickering at idle but less frequently...or so it seemed,
Drove it a little over 200 miles. At highway speeds was fine but light lit at about 3000 rpm or under. Drove home the last 25 miles with a solid light at all rpm. No noise or change in driveability.
Next morning was fine. Short in town trips and no oil light. Drove out of town and 20 miles later, light at idle. Driving home light came on steady and engine started clattering loudly at idle (albeit normal at speed).
Drove home, and at that point I was sure damage was definitely done.
Started next morning quiet and drove perfectly around the block!
Any suggestions?
...something broken in the oil pick up? Why would the oil darken after so few miles?
Can the oil pan be removed from under the car without taking half the car apart?

 

Pull the filter off and check that the plastic return drain valve is still present in the filter housing assembly (attaches to the block). You may wish to remove the cooler, and whole assembly from the car for inspection.

I've recently read on FB groups about this being a significant point of failure and result of exceedingly low oil pressure.

 

Okay....I don't have the oil filter housing issue. After more driving , I've come to the conclusion that it looses oil pressure if I wind the engine past 3500 or so RPM.
First it will come on at idle, shortly there after steady light and progressively worse engine clatter. Next day , quiet as a mouse/.
Any ideas? Oil cavitation, perhaps?
Anyone have similar issues?

 

Since you've got fresh oil & a filter, I think I'd get a real oil pressure test done with a real pressure gauge. Any garage should be able to do that.
My understanding is that the MINI oil pressure sender is just an on/off switch set at about 5 lbs psi - you should be looking for about 50 lbs psi driving normally.