Recently at Driven SD we had a request to replace the rod bearings on an BMW E46 M3 as a preventative measure. So we thought we'd share what normal bearing wear looks like at 169,000 on a BMW S54 engine along with what a new bearing looks like.
On the left are the upper connecting rod side bearing shells, and on the right are the lower connecting rod cap side bearing shells. The uppers definitely wear more from the downwards force of the power stroke, but that's normal on these engines.
There's a lot of debate about replacing BMW rod bearings on these and other S engines at certain mileages. While we don't recommend a certain mileage to do this BMW service at, if you've had the car for a while and plan on keeping it, a rod bearing replacement or upgrade may be a worthwhile investment.
And if you really want to nerd out on some bearing wear and rod bearing failure analysis, this is a great resource.