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I go to Idaho and Montana several times per year.. My last trip showed that the AEM update REDUCED my normal fuel mileage about 10% overall or more. The trip is spend about 60%+ of the time at 83 mph since the speed limit from southern Utah to northern Idaho is now 80 mph in most places.

This trip I did have four people on the return trip, a couple of extra small suitcases and a moderate headwind in southern Utah...but the mileage has been down at home at city speeds as well.

This 2019 trip shows 2256.6 miles, 19.9 mpg- 62 mph average and 36:03:01 hours.

The other photo shows late 2018 trip to Idaho...only one way as I did not see the need previously to save these.
 

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I've noticed the same thing. The issue (I'm pretty sure) is they've changed the shift points and shifting algorithm. I can tell that my truck doesn't shift or hold 8th gear as long and downshifts. I watched my mpg's drop every time it downshifted where it didn't before. It can't keep getting the same mpg's before and after. I wonder what FCA will say as their claim was that mpg wouldn't be affected. Another lawsuit?
 

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So it would probably have done 22 mpg before the AEM?

That's alone is not really that good. When you get above 75 mph (3:55 rear end ratio) that fuel mileage does drop. Yours just seems to never have been very good in the first place. Now losing more is just more bad news. Even with the 3:92 rears end ratio you were not so good.

Assume that from California you are running a stock ECM as you are running the AEM one now. Guessing that in addition to the high speeds there could be something else detracting. Could be tires, tire pressure, a drag somewhere, heavy foot syndrome at starts and stops, or ....

Hope you find something as you are somewhat below EPA ratings and the normal.
 

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I've got a 17 so I should have the same tune you do. I got 26 easily and can squeeze 28 if I drive it. I dont like staying above 80 as the speed limit here is typically 70. The 3.55 is a great gear around 60 to 65 because it keeps the rpm low enough while not fighting the wind. The 3.92 ratio even though the rpms are higher tend to get better mpg because it is a higher torque multiplier and helps with the wind resistance. What I'm getting at is, it's hard to compare apples to apples when the environment is involved. I have a 700+ mile range on my stock 17.

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Just got done with my first long trip since having the AEM done 1 month ago. It was approx. 500 miles, got 25 according to evic there and 28 on the way back with cruise set between 70-75. This seems about normal if not better to me. I have stock sized A/T tires. 1/4 tank left after 500 miles seems pretty good to me.

I don't really drive daily in the truck anymore as the drive is 30 miles downhill and 30 miles uphill, but it shows about 19mpg.
 

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I just covered half the country with the AEM tune, and it blows. My truck never got great mpg before (20-25 city-hwy) but now I get 20hwy and about 18city. I am very mpg minded and coast as much as possible. On takeoff, I believe it's better to get up to speed faster and get into the sweet spot sooner, but I'm not mashing it all the way or anything. I towed a 6000lb load from AL to Miami and got about 11mpg at 65mph. It decreased the faster I went. Drafting behind rigs got me 11mpg at 75, and that's what I did A LOT. I also noticed that I can't backup with the door open. That is SUCH a negative for me, that I'm thinking of disabling my door sensor on the driver side. After teh AEM, the gasoline models seem much more attractive. Maybe it's time for the GDE, but if I sell this, I can get a used Tundra with less miles and less headache and more reliability. It'll cost the same to operate, and much less to change oil. This truck doesn't stand out against any other anymore. It used to be the most fuel efficient, but no longer :( very sad.
 
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