[AndyW]

Update: So, the mystery gets more muddled. Got the results of the latest 1000 mile sample. Lead down to 10 ppm. Previous 1000 mile sample was 32 ppm. Blackstone still suspects it was from race fuel I was using last summer for several track days that is just diluting down.

I also discovered that sometime in 2011, BMW shifted to Aluminum/Tin Rod bearings due to new EU environmental regulations. As my car was built in 2011, I have no way of verifying what they are made of short of pulling them out. Blackstone is aware of this change and tends to think, given the data, my bearings are actually Aluminum/Tin since lead was zero in all samples before I tried race gas. I am inclined to trust their expertise and it would save $2000+ in parts and labor doing rod bearings that I probably don't need it. But it's a big risk that could end in a blown engine the first track day of the season...sigh.

Pondering this, I think the best course of action is probably to go another 1000 miles and take another sample. If lead is still 10 ppm, that makes it pretty clear that Blackstone is right. If it goes up, then it's probably the bearings. If anyone sees holes in this logic, please let me know...