Chrysler 2.7 V6 (EER)

Chrysler's 2.7-litre DOHC V6, in the Intrepid, Concorde, Stratus, Sebring, Magnum and 300. It has one of the worst reputations of any modern mass-market engine and the reputation is earned, so the first question about any example is its oil history — not its mileage.

It sludges. Oil degrades, thickens and blocks the pickup screen, the engine is starved and fails, and it happens on cars that have been serviced to the manufacturer's stated interval. A 2.7 with no service records is a risk regardless of how it sounds, because the damage accumulates silently and the first symptom is often the last one.

The mechanism that makes it worse than an ordinary sludge-prone engine is the water pump: it is inside the timing cover, driven by the timing chain. When its seal fails, coolant goes into the oil rather than onto the ground. There is no puddle, no temperature warning at first, and the contaminated oil then does in weeks what neglect does in years. Coolant loss with no external leak on a 2.7 is the water pump until proven otherwise, and replacing it means going through the timing cover.

Beyond that, the crankcase ventilation blocks and the timing chain guides wear. Short oil intervals with the correct grade are not cautious advice here — they are the difference between the engine lasting and not.