Seems that analysis for bismuth may soon be necessary in UOA to detect bearing wear in lead free bearings. From: http://www.automotiveproductsfinder.com/Articles/AR2007/MAR/AR-09.asp ".......Daido Metal has developed a completely lead-free bearing consist-ing of a copper-tin-bismuth-molybdenum carbide bearing alloy on a steel back with bismuth/silver dual layers as an overlay. The bearing is not just lead-free but also suitable for high specific load conditions. According to industry sources, the newly developed bismuth/silver dual overlay exhibits anti-seizure properties equivalent to a conventional lead alloy overlay, which is itself especially resistant to seizure. .....................Daido Metal has the top market share in Japan for plain bearings for engines. ........" This from an April 2009 SAE abstract by Daido Metal: ".......Recently, a lead-free Al-Sn-Si alloy bearing with metallic overlay has started to be used for a portion of automotive engines. This bearing has good anti-seizure and excellent running-in properties, and is an environmentally friendly alternative to the current copper-lead alloy with lead based overlay.............It is clear that the current lead-free aluminum alloy bearing is not satisfactory with respect to fatigue strength in some cases, and requires higher strength under the higher temperature conditions. Based upon this background, a new lead-free aluminum alloy bearing with metallic overlay has been developed, which is an Al-Zn-Si alloy bearing with a plated bismuth overlay via a silver interlayer for securing a good running-in property........."