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.