yeah I dont believe it either. I dont know what the previous owner had in it or what. But I do know how to hand calculate it. But this truck gives me better mileage than my dads 08 6.7 mega cab 2500 with deletes. I have stock tires. I dont drive it hard. 4.10 gear ratio. I had a 7.3 with 6 in lift and 35s could never see better than 15 on highway. take in regards I live right next to highway so MOSTLY everything put on this truck is highway mileage. I love this truck so far.

Right, but unless you fill it like I was mentioning, the amount of fuel is different every time that's what the issue is.

Red flag! Now I don't believe 4.10's can achieve anything close to 20mpg. I ain't sure, just I don't believe it now that I know the gears

I honestly don't believe it myself...the previous owner may have something i haven't found yet.

Personally I get 300+ to the half tank mark with a 38 gal tank. Fill it up, drive it and then tell us how many miles you have driven.

Mine is similar, 250-300 miles when the needle is between 1/2 and 3/4, then she drops like a damn rock after that. I usually end up around 550 when I pull into the pump, most I've ever put in was 32.5 gallons, I NEVER let her get too far below 1/4 tank (~17mpg hand calculated). I'm mad at myself if I let it get to 1/8 tank before I fill.

we just did a 1600 mile trip with my new truck estimated mpg said 16.5 hand couclulated out was fairy close everytime i filled up withing .1-.3 everytime

This is really interesting. I have a 4X4 CC DRW with 4.10's. I get 20mpg or better on the highway at 60mph as well. If I really try for mileage allowing the truck to slow to 55 at times on hills and such I can get around 22mpg.

At 70-80mph over a 1250 mile trip I got around 18.5. Anything above 60mph with 4.10's kills mileage. So maybe 60 is just right in the sweet spot for my gearing and tire size?

I run 70+MPH turning 1930+ RPMs and it's pretty decent MPGs for me. So if that speed has you under 2K rpms that's the reason the MPGs are high.

I get just under 700 miles on a full tank. I average 19 and 22.5 highway at about 65. I will see about 15 loaded with about 10 round bales. This truck is the best so far no problems and pulls like a train. when I am at 60 mph my rpms are pushing about 2k rpms thats why the fastest I push this truck is 65.