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Discussion Starter · #5 · (Edited)
I was getting 14.9 until my engine light came on. I replaced the oxygen sensor right away. After I replaced it my mileage got worse to around 10 but after about a month now it has only gone up to 13. I don't get it. I've heard that a bad sensor can cause your mileage to get worse but not the other way around. Any clues?
 

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Hi and welcome

Disconnect the battery for about 15 minutes, to let the ECU "relearn" the new O2 sensor. That might help.

Or, you've got a heavy foot LOL

Nowadays I average high 16-low 17mpg daily driving, but when I first got my truck I was in the 11 range because I drove it like my old car!
 

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Being a new member I would like to list my truck at the bottom of my posts like you have. Can you tell me how to do that? Thank you
It's a signature, in your user control panel. If you don't have the option yet, I think after you have enough posts it opens up and you can add your own sig
 

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Great advice by raine about the ecm reboot. I posted in the past about a cel for an 02 sensor that cleared itself after I replaced the fuel filter. The 02 sensor was just reacting to the low fuel pressure from a restricted filter. You also could have a bad or poorly made sensor if you bought one that wasnt oem. you also need to assure all of your grounds and battery connections are clean and tight and that your battery is strong, cause things malfunction with an old or weak battery. These are just basics, hopefully someone else can add input or past experiences to help you achieve better mpg. Unfortunately the previous posts indicate poor mpg is common. Good luck!
 

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Discussion Starter · #12 ·
Thanks for the advice. I rebooted the ECM, battery checks out and cables. OEM sensor. If the fuel filter was bad it wouldn't the mileage still have been the same before the new sensor was installed. I am getting about two mpg less. Was 15 now around 13.
 

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I have also read in several places that it is possible to have communicatiuon issues between the upstream and downstream 02 sensors when one is old and one is new. Before you worry about that, be sure to cover basics such as air filter, clean the throttle body and inspect any vacum line you can access and its connection for cracks and dryness. Try buying different brands of gas. I swear I get better gas mileage when I buy it at a 7-11 near work (dont know what brand it is) as opposed to the name brand gas in my town.
 
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