The six-cylinder engines are virtually bullet-proof and regular servicing will see them cover huge mileages. The M110 twin-cam ‘six’ gets a bit rattly with age – irregular oil and filter changes leads to worn timing chains and valve-gear – but will still solider on, while smokiness is often cause by hardened valve-stem oil seals. Look for oil leaks caused by perished gaskets or a cooling system past its best, but there’s little else to worry about here and you should see 100,000 miles before any sort of overhaul is due. Parts availability is generally good, too.
six-cylinder cars can cover at least 100k miles before a major overhaul is needed.