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Sudden loss in mpg efficiency

Jeremy Salyers
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Jeremy Salyers New Member

Jeremy Salyers

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Happy Holidays folks! Hope everyone's well and warm.

 

I've got a 2013 Silverado 5.3L with 173k on the engine. I bought it at the beginning of the year with 150k on it and have been quite pleased with it till recently when the mpg went from an avg of 16 in town, down to 12. I had spark plugs replaced back in Sept, keep the oil and air filters clean, and the tires at proper psi. Can anyone help me determine what the culprit is for my recent loss in gas mileage? 

 

Thanks in advance 

richard wysong Senior Enthusiast

richard wysong

Posted
Posted

Welcome to the forum! could be lots of things, brakes dragging, trans slipping etc. Any codes? Did you change anything before the drop? You may need a scan tool that does live data and trans data to figure it out as some sensors may not set a code if they have not failed but are sending false data to the PCM

CamGTP Senior Enthusiast

CamGTP

Posted
Posted

With a scan tool I would want to be seeing what the truck says the alcohol content of the fuel is.

 

Many trucks in those years can suffer from the problem of the virtual flex fuel sensor becoming incorrect and thus using more fuel than normal. There is no actual sensor on the truck, it's a value that is created based on the readings from the o2 sensors themselves and sometimes it goes wonky.

 

If the value is something dumb like 30-40% when the fuel you are running is standard E10, then you have a problem. A reset of the alcohol content would be required with a scan tool.

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