Chrysler Repair: 06 T&C Limited 3.8L (68,000 miles), o2 sensors, fuel mileage

Question
QUESTION: First off, thanks for helping me a while back with the stumbling issue. The O2 sensors cleared up the problem just as you stated.

I meant to ask you this question when I asked about the stumbling but forgot. I am only getting about 15-16 mpg on a tank of gas with a fairly even mixture of small town city/highway driving. I have changed both O2 sensors using Mopar sensors, changed the plugs using oem Champions and plug wires. I am not a heavy footed driver at all. There are no computer codes and the vehicle runs fine now except for the mileage. Have you ran into this mileage issue before or possibly have an idea of what the problem may be?

ANSWER: Fuel mileage is a big concern these days. We have more than a few enquiries everyday from people on this subject. Sign of the times I suppose. I'd wait until the computers adaptive memory has relearned the new fuel mixture calculations from the new O2 sensors before you get to concerned with fuel mileage. The O2 sensors have a huge affect on how much fuel is fed to the engine and once they are changed the PCM still works off the old adaptives for a while, so in most cases fuel mileage will suffer in the short term.

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QUESTION: Thank you. Approximately how long should it take for the computer to relearn the new calculations? Should I disconnect the negative battery terminal for a few minutes to reset the computer? I just need to know how long to wait before deciding if there is something else going on. Thanks for all of your help!

Answer
Disconnecting rhe battery will force the computer to perform what is called Memory Reset which does nothing more that erase all previously learned values and start its learn process. This will speed up the process of learning a little bit but not much. I can't tell you how long it will take, it all depends on how you drive the vehicle and how many adaptive learn "boxes", for lack of a better term, are filled. Generally it should be completed within one tankful of fuel.