89) If the spark plug deposit indicates black coating of soot, it indicates that the engine has been generally operating on

Answer is:

too rich mixture

Answer is:

Answer is:

Answer is:

oil strainer - oil pump - relief valve - oil filter - cylinder block - cylinder head - oil pan

oil pump - oil strainer - relief valve - oil filter - cylinder block - cylinder head - oil pan

oil strainer - oil filter - relief valve - oil pump - cylinder block - cylinder head - oil pan

oil strainer - oil pump - relief valve - oil filter - cylinder head - cylinder block - oil pan

Answer is: