Came back from Austin a few days back, 1200 mile round trip. 2007 base cooper running rough last leg of the trip. Bought the coop in march. Went over it except changing the Plugs. Any way went in to replace plugs and two plugs were at hand tight if that. Plugs were fouled some oil around plug ports. I have heard they come loose. Sure enough they were. Now i'm getting 57 miles to the gallon from 46. This could explain some loss of oil also. set torque to 19 ft pounds on plugs. Everyone be sure to check your plugs periodically. Also Had a small drip coming from water pump when i got it. Progressively got worse. The leak was the rubber gasket. Spent 140$ on pump and pulley and serpentine belt. replaced myself. No more leaks. I like the cooper, but damn the the ******* little things that go wrong with it. This is my commuter car.

 

I have the R56 S The hard pipe sometimes goes out also with that water pump. I just got done with a full hard water component replacement (water pump,electric aux water pump, thermostat housing). I saved the old parts aside of my regular water pump and hard pipe). I used standard thread lock on the studs and superlube silicone grease on all the o rings. I set my torque on my plugs to 14 pounds as to not destroy the aluminum threads. I make sure never to use die electric spark plug grease on the plugs humidity will collect under the coils and foul a coil and a plug out. If you don't have extra coils and plugs around you may think it is something else; When you get misfires. In my situation it is coil or spark plug most of the time.
I change my plugs regular not every 50 thousand. Timing Chain might be going out that is one sign of plugs going bad. But in the mini world it would be like once a month you have to get new plugs.

I get plugs about twice a year not counting the ones in the car. I save the old and gap and attempt to use later which often does not perform like new ones.

The first thing I ever bought for my mini cooper back in 2011 was a new alternator in early 2012 which was the re vamped version; And a double pully wheel that powers the water pump. even though the old one was not bad. Just two weeks ago I found the original in the garage compared it with the one I had bought and the original still has the hatch marks on the steel wheel that powers the new water pump pully wheel. So it's good to save stuff when you can and not to discard old items if you don't know for sure but to keep on top of recall and revision list. You know mini cooper actually came out with a bung to put in the rear of the valve cover a genuine mini cooper plug for the rear pvc. That helps the plugs from fouling so often and solid timing chain with the re vamp tensioner bolt. In fact that's when plugs stopped having problems with mine so much timing chain tensioner bolt version 2. and the plug for the pvc.