there is thick blue smoke coming from the tail pipe after the engine has idled for several minutes. what is…

Brief Explanations:

When piston rings are worn, oil can leak into the combustion chamber. When the oil burns, it produces blue - smoke. A broken main bearing would cause engine knocking, reduced oil viscosity may cause oil consumption but not typically thick blue - smoke right after idling, and a bad oil - pan seal would cause oil leakage under the engine rather than blue - smoke from the tailpipe.

Answer:

C. worn piston rings