How often should oxygen sensors be replaced?

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On older gasoline-powered motorhomes (such as 1988-1995 Fords and 1990-1995 GMs), replacing oxygen sensors at specific mileage intervals was often recommended. On newer models with OBDII self-diagnostics, the sensors are designed for a service life of 100,000 miles or more; so, there are no scheduled maintenance intervals listed for them. However, many experts recommend replacing high-mileage sensors to regain performance and mileage, especially on pre-OBDII models.

When the old sensor is replaced, it should be inspected. Heavy black deposits indicate an over-rich mixture; dark brown may indicate high oil consumption; white or reddish deposits may come from fuel additives, while light-colored or grainy deposits indicate a coolant leak.