Originally Posted By: wn1998
looking to get the best mileage out of my jeep and currently have 145k on the jeep and about 40k on the current set of 02 sensors. My buddy swears that replacing your o2 sensors every 30-40k is a must to keep your mpg acceptable.
My jeep only has 2 02 sensors so I would only be looking at $80 to swap them out but is it worth it?
Well as much as it sounds like I am being "Angel Gabriel's Advocate" I am compelled by a sense of right and wrong as well as economy with regard to the replacement of any sensor.
Sensors are designed by engineers and tested by engineers and they do not attempt to produce sensors with a limited useful life or it would be in your owner's manual. They would warn you to replace them.
Case in point: I have a family member with a 2001 Nissan Maxima with 104,000 miles on it. It has been suggested to him 4 times over the past 9 years to replace sensors by mechanics. None of the mechanics are Nissan mechanics. Hmmmm.
A Nissan OBD2 system installed in cars since 2000 will tell you if the sensor is bad. If it doesn't tell you, then the sensor does not need to be replaced.
Logically it follows that if Nissan can develop a sensor that even a stupid computer can determine if it requires replacement, then any sensor can be tested to see if it requires replacement.
If the "mechanic" (I use the term loosely, with generosity) can show the owner the test procedures he has put the sensor through to determine that it is not functioning, then he should be taken at his word and the sensor should be replaced.
However, I seriously doubt that the mechanic suggesting replacing the sensors will be able to test it. The great majority will not know where to begin.
The reason why non-dealership repair locations want to replace the sensors is when the sensor is replaced to new, the ECU is reset to "no codes" and until a little time has elapsed and a code producing event has been detected, there will be no "service engine soon" light on the dash. That gives enough time for the owner to pay the bill for parts replaced that didn't need replacing until two weeks later when the sensors record an event such as "intermittent high voltage detected cylinder 4" from the high voltage coil causing spark plug misfire.
Back to the family member: after being told that the "sensors need to be replaced" by a non-Nissan Garage (and a good one at that), after two tankfuls of gas were burned through with my suggestion to use Gum Out with Regane, all the lights, hesitation, stalling and bogginess disappeared and the car is running like new again, WITH NO LIGHT ON THE DASH...the owner's exact words..."like new".
Don't replace a sensor when it puts out an OBD2 code or they test it electronically in front of you to justify the expense.
The sensor is communicating what the problem really is and until the garage gets up to the present day technology, they'll tell you you need new sensors, a new engine, a new transmission, a new car in that order.
