[orientalexpress]

Thanks very much guys. The light was for the radiator fluid which I added.
The car never overheated, and I just put a couple of quarts of oil in a month ago.
It's still under an extended warranty that I bought. I will be taking it to BMW dealer asap .
I'm kind of frustrated at 40k something like this is happening. 
I should not have bought a BMW , as I need low cost maintenance , and reliability .
My last vehicle was a Lexus suv . (Rx300) at 130,00 I never had a single problem with it . I think I prefer the seating position of an SUV as well.  I'm only 5'3" and I feel like I'm getting in a small sports car, which is fine for a twenty min. ride, but driving it 5 hours for Uber in the city is getting old . Thinking about swapping it.
When the battery went , I called BMW , they said between $575-750$ . I was like , "what have I got myself into ?  I got one at Autozone for $180.

I'm still driving my 1998 lexus ls400 with over 200k on it,the most expensive maintening is Timing belt change at 140k cost $1100.00 and 4 brand new michelin tire cost $1200.00 install. it's run like the day i got it except maybe a little rattle here and there.I'm waiting for mine to break down so i can buy another lexus 

[thunderbrick]

Eight years ago I bought a used '05 525i, and in all that time (80K miles) I've had one repair; alternator went out early this year.

The rest has been routine wear-out, tires, brakes, etc.  Still drives like new.

[kenreau]

Code read : Cylinder 4 misfire.
Spark plug issue?
My mechanic was saying some type of plug needs to be replaced .

Yep, that is what I was referring to earlier, possible coil pack on cylinder.  Easy fix, like changing a spark plug. 

Another issue of possible concern is carbon build up in the induction / valve area.  Its not unusual for some of these newer FSI engines need a valve/head cleaning about every 50K miles.  If you just want to fix it and sell it a.s.a.p. fix the coil and peddle it.  If you intend to keep it another year+, I highly recommend locating a shop that performs BG products induction cleaning.  Google search it.  They can scope it and see if it is built up to a point needing cleaning. The alternative is a walnut media blast to clean out the head (more expensive).

[DaveC113]

This seems ridiculous...  over-expensive batteries that need registering and do better with the owner hooking up a battery tender. Cylinder heads that need cleaning every 50k mi...     

[Bob in St. Louis]

I highly recommend locating a shop that performs BG products induction cleaning.  Google search it.  They can scope it and see if it is built up to a point needing cleaning. The alternative is a walnut media blast to clean out the head (more expensive).

Whether or not this is the solution to your particular problem I don't know, but I will say that BG makes some amazing automotive chemicals. I've been using them for many years (except the last nine) and they perform as advertised.

[FullRangeMan]

One thing I do not like in BMW engines is that the engine block is a sandwich, aluminum on the inside and magnesium on the outside.
The Magnesium is lighter than aluminum but is easily corroded by coolant engine.
I suppose all modern engines are this way.