Q&A

I worked at a dealership for over ten years and never saw a problem with a piston or a melted converter. Yes, I have replaced some cats on a few of the cars but not because a melting mostly for low eff.(If they are having issues I bet $100 that the cars were modified).
Only timing chains that I have seen are on the m62 and every one I have taken apart to fix had about 1/2 inch of sludge inside the engine. Likely from them running conventional oil or just never changing it. All the engines I have taken apart with normal 15,000 mile oil change interval WITH good synthetic oil are spotless!

I work for BMW for 25 years Master BMW Technician /Instuctor and research.Dureing many years only seen damage to pistons when vehicle been modified (NOS and other mods) on N62 or N62TU. Yes seen CATS go bad ,but BMW has address due to DME (Engine module) Software Issue. Other Issue due to timing chain failures is always due to vehicle not maintain (exceeding oil services(or none) or using incorrect oil (generic) and using none BMW Oil filters Causing scavaging or inefficient oil pressure). Oil Services Should Be done every 6 month to a year or required intervals which every comes first. Seen many come in for connecting and main bearing Knock noise due to Use of to thin of oil as 0-40 full synthetic which cause to throw bearings. As Instructor knowing we would not recommend or suggest to us other than factory recommended fluidor intervals. (If recommend changes are require a SIB would be posted be Manufacture and to the Public) If well maintian and kept up with maintiance have worked on and seen N62 and N62TU Running strong with 250,000 and 445,000 miles. Have check bottom End and minimal oil residue in Oil pan or valve train.