3.0 duramax
 

I just did a long tow , 6000 miles round trip. South Florida to Atlanta and then to San Diego. 21.3 mpg towing a 22 Donzi Classic. Fuel tank was close to full. That was on the way out and I took state roads or fm roads until Tucson and then 10 to the 8. On the way back a storm was coming and I ran north on 15 to St.George Utah and then went south through Page Az and picked up 40 outside of flagstaff. Return trip was 20.4 mpg . Wanted to share the excellent fuel economy. Now the def is a different story. Towing uses a lot more and I went through 7.5 gallons.

thats awesome! 21mpg towing! i can barely squeeze that out of my gasser truck on cruise control on flat land empty!!
What truck? SUV or pickup?

our AT4 got 30-37 going to pa for NHRA this weekend the engine is so impressive i,m trying to buy 2 for a Viking repower project it comes alive when towing like a tractor puller i just found the boost spec on it ........almost 45 pounds no wonder it act like a tractor puller! awesome engine

Chevy Silverado crew cab , high country. 2 wheel drive
https://cimg3.ibsrv.net/gimg/www.off...3c6c9a176.jpeg

Return trip
https://cimg6.ibsrv.net/gimg/www.off...1d6dace26.jpeg

Those are impressive numbers while towing. Id be interested to see hand calculated numbers to compare to the trucks system.

for those that have a 21 3.0 theres a computer update to fix turning over but no start issue

Onboard vehicle MPG calculations are notoriously inaccurate. Did you do the long math?

exactly. I always hand calculate my fuel mileage.

Me to,,,,,,,, only way to do it on my 1996! LOL