I just filled my tank and drove back from the shore and went a total of 66 miles and refilled once I was back home it took 3.08 gallons for an average of 21.43. My evic said 22.3. This was with a semi light foot with an avg speed of 70 to75. I can't complain on the highway these trucks are great, just wished it did a bit better around town. 4x4 quad cab 3.55 5.7

 

Nice mpg!

I have a CC, 4X4, Hemi, 3.55 and have averaged 20.1 mpg on long trips and 19.8 while carrying about 500 lbs in the bed, all between 70 and 75 mph. Average around 14.5 to 16.5 with mixed driving around town So i am pleased with mine, I also tend to try and keep a light foot on the pedal or cruise control whenever I can.

 

I definitely did better mpg before my exhaust. It sounds too nice and I keep flooring it.

 

I edited the picture in the first post to reflect the ACTUAL MPG (thanks awful knawful)

While I am disappointed to NOT be over 20mpg, which I always thought was too high, but who checks there own calculations anymore, haha. I am still glad to see it better the old truck, which means I am paying no more to fuel now, then before, but have a much nicer, newer truck to drive.

 

to have 390 hp and be able to get this good a mpg in a truck this big is nice. i think your truck will get better as it breaks in some and loosens up. I have almost 18000kms on mine.

 

What year and engine was the Sierra? I had an 06 Chevy Ext cab 4x4 310 hp 5.3, 3.42 gears. Great mileage, or so I thought, at 74 mph. Now a quad cab 4x4 Hemi with 3.55s will out do it for mileage, if the tires aren't too aggressive. the Dodge is also a good 300 plus pounds heavier, with the b pillar to mount the back doors on, and a whole lot safer, in a head on accident. Less wind noise, less shifting to get up the the steep hills, and a much better all around driver. Chevy had put some very street tires on there to get the mileage, as opposed to my current AT/S s and the Good Year RT/S s on my Dakota I hated those Ext cab doors, like if my wife and I go to the dirt track, and I want to stay to the end, if she's tired and wants to lay down, well, its a pain to shut the doors from the back! Or the fact the ext has alot of flex...broke a cab / frame mount bushing, and I don't even go playing off road! Thats just from a 2000 mile trip on highway to Colorado!

 

It was a 2002, ECSB, 4x4, 285hp 5.3, 3.42 gears. And as you can see from the spreadsheet, the same or maybe a little less then the new Ram 1500 I have now.