Arith2 It sounds like the current "5,000" mile oil was not the cause, but there was damage already done to the engine while you were on the new oil and it was just a matter of time before the rods went. Your oil is the scapegoat.
It's hard to diagnose where the rods went bad, but lots of users have been running Liquimoly GT1 10W60 on their S54 with no problems. Personally I've ran Liquimoly on my race car for 2 years and I see up to 280+ in oil temps on track - 0 issues. I still beat the crap out of my engine and my engine is still healthy.
If you want to run a different oil, I highly recommend Redline 10W60 as well. James Clay at Bimmerworld will tell you it is the only oil he will use on his cars.
Just to touch on some possible causes of premature failure, it may have been the following:
- Running high RPMs while engine is still cold
- Low oil pressure due to clogging
- Degradation of oil compound due to overheating