Hahahaha... I truly hope you're being sarcastic.
I'm just stating that with the larger displacement the usual is a lower fuel mileage... Of course there are thousands of factors that play. It would have to be the same vehicle setup with the only difference being the engine.

In your previous statements you were talking apples to oranges. It goes along the same lines as comparing a gas engine to diesel. You can't. The are different. Same goes with the 5.3 vs 6.0. Yes, they have interchangeable parts. But they are still different power/torque providers, fuel delivery amounts, burn rates, compression ratios. The list goes on. Thats all I was commenting on. This thread is coming from a 5.3 stand point. Your specific fuel numbers can't be compared to it.

 

Again, the common rail Cummins trucks DO NOT get 24-25 at 70...Their mileage readouts are notoriously inaccurate...If your numbers aren't hand calculated over a long distance, then they don't mean anything.

As for 25 in a 6.2L truck...were you coasting down the side of a mountain?

 

I can get 17-18 in the city with a cai, bb 93 tune, headers, muff, and a pretty light foot (6.2)

 

Blackbear. Let me re-fraze that, I didnt help at all at first, but after a bolt on or 2 i noticed a slit raise, maybe .5 to 1 mpg at best and thats on highway doing 65. I love the tune no doubt! its best mod ever. just havent see the mpg increase most people claim

But i do have 33'' mudgraps and rockstars so they are heavy as ****.

 

Nope No mountains in Houston,TX. Just cruising up 45N and 288S You'll also have to account i'm running on 245/70/17 general Grabbers that are harder than the concrete we drive on and they are low rolling resistance tires. When i had my factory 20's i could manage 22ish.

Also i took a roadtrip to east coast when i had 22's with 305/45/22 which is about 33" tall. I had cruise set at 78mph and got 17.4mps!

 

One of the exact reason why I was saying to get a true mileage reading. It would have to be 100% highway with a full to empty tank and 100% city full to empty tank. Even our readouts are known for being 7 - 11 % off. Thats quite a bit when calculating miles.

I personally do a pretty even mix of city vs highway driving and get right around 400-430 miles to a tank. That to me is a more tangible number since there is a combination.

Its not like we as owners bought these vehicles for fuel mileage anyhow. I bought mine to pull things and have fun. My cheapo motorcycle is the fuel saver.

 

i get 18-19 highway with 22's, gears, cam, and full exhaust

 

Just in case you might be considering a tonneau, here's one that might interest you. https://www.performancetrucks.net/fo...5/#post4849052.

I have received a few calls from customers saying they've noticed about a 12% improvement in gas mileage. Our system weighs about 55 pounds total.

I adjusted my driving habits to improve my mileage. Depending where you drive, you may find that coasting more, braking less and slow acceleration will help a lot. Anticipating red lights, instead of trying to beat them will yield dividends too.