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Discussion Starter · #1 · (Edited)
I am a new member, poster, so please be gentle....

I have noticed a sudden and rather dramatic drop in MPG. According to the Overhead, my average MPG has dropped from 19mpg to 16.7 mpg with no change in driving habits (lots of highway). I realize that these numbers are not worth much, but my calculations based on odometer have dropped proportionately. The ONLY thing I have done differently has been to replace my old P265-70/17's at 35psi with LT265-70/17 tires, inflated to stock pressures. I would not have expected a significant changed either way by doing this.

Looking for suggestions. The only other thing I have noticed is increased transmission slippage (original 47RE). That repair is in the works.

Thanks, in advance.
 

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Have you noticed any white smoke and / or rough idle at first start of the day? Could be injectors going south.

The LT tires are a little heavier, but I don't think enough to cause that much drop in mileage. If you trans is slipping that could do it. Are you buying fuel from the same source you usually do? Fuel and air filters clean?
 

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Discussion Starter · #7 ·
I have noticed the idle a bit rough lately, but no smoke. Air filter is clean, but probably due for new fuel filter. I have a small circuit of fuel stops I frequent, and that has not changed in 2 years for the most part.
 
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