If the oil light comes on whilst driving, then the critical question is whether it is the oil level or the oil pressure that you are being informed of a problem with.
I suspect there is something other than just the timing chain at issue here.
It may be that oil is being burnt or leaking - in which case the level will have dropped, possibly causing major damage. If, on the other hand it is oil pressure, then that would indicate a blockage (or partial blockage) somewhere in the engine so that oil is not moving through the engine.
A little bit about the timing chains, and how they are lubricated : Basically, the timing chain is sprayed with oil on these engines, through a few very fine nozzles. If crud/sedimentation is in the engine oil, then it can quite easily block those nozzles. Leading to a lack of lubrication on the chain, the chain then fails.
As such, a lot of BMW owners (myself included) get oil and filter changes done every 10k miles, rather than BMWs usual 18k miles. It's also critical to get the old oil drained FROM THE SUMP (the proper way) rather than pumped out via the dipstick hole (the cheapest way) to assist in moving any crud/sediment from the oil. In addition, going for the best quality of oil, and the proper BMW filters, certainly won't hurt matters.
Unfortunately, especially if you've had a 'groupon cheapie' deal on a service, you'll probably have had the old oil syphoned out, a cheap generic filter fitted, and the cheapest possibly grade of oil put in. A classic case of 'you get what you pay for'.
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