The past 3 weeks in South Carolina we have been in the 95 - 100 degree weather and I have been running the air everywhere I drive, but is that more than likely the reason for a dip in mileage from around 14.2 to 12.3??
No issues with the truck or codes.

 

I've read the Hemi doesn't like hot air. That seems to be confirmed by the way my C runs in really hot weather. That's less than a 15% drop. The A/C could be the primary culprit. You must drive pretty slow to get 14.2 mpg.

 

thats better than me, i average 9- 10 in he city. complete BS. All i have is a level and 34's. Unless my over head is completely off. It still seams like I fill her up alot. Im hoping the culprit is the serpetine belt haha, im just kidding. I replacing it today but i still wish the belt caused poor mpgs.

 

If you're relying solely on the O/H console, I have disappointing news: it's usually optimistic. There is only one valid, accurate way to determine fuel mileage.

 

Mine was actually reading low the last time I checked it. It said 17.2 so I did the math and it was actually 19.2. I was pleasantly surprised!! I am trying out the new Mileage booster tune on my DSP. This is with the MDS off. I like the mileage, but I forgot how bad the torque management is when not running the 93 octane tune.
Did you get gas at a different station? Perhaps the fuel has more ethanol in it which kills mpg. I see very little mpg difference when running the a/c.
Time for new spark plugs perhaps? Is there close to 30K miles on them?

 

My VIC says I am getting 13.8 to 14.2 or so, but doing the math at fill-ups = 11.8 to 12.4 depending on how I drive it. I wish it would get 15, but I guess that is a pipe dream. My 00 wrangler gets 16 mpg's with 4:88 gears and 35" tires.

 

mine reads 9.4 in the city so im hopping its underestimating my mpg's. I would do it on paper but I always forget.

 

Click the "fuelly" banner in my sig and join up. Makes the mileage computations fairly easy.

 

What Sig? Your using that mobile site aren't you... it convienently forgets our banners.

 

Not using the moble version - I do often supress my signature on additional posts in the same thread. Take a look at my first post. Anyway, it's fuelly.com You can enter data from your mobile phone right after a fill-up. I just grab the receipt and enter new data from home, since I have to make the calculation to compensate for my odometer error.