I don't know exactly what time period it applies to, but I think the bearings in an auto engine sometimes contain lead, which is a (maybe not the only) reason t

I don't know exactly what time period it applies to, but I think the bearings in an auto engine sometimes contain lead, which is a (maybe not the only) reason that used engine oil may be considered hazardous. I am aware of an example from the late 80s that seems to have lead and one from the early 2010s that doesn't.