alrght just filled up again. my overhead display was reading that i averaged 18.3 mpg. my hand calculated mpg is 17.5. so it is off by a little more than half a mpg. not to bad. and that is also a 1 mpg improvment over stock. that was mostly all in the 65hp dd tune. this tank will be all in the 80hp dd tune and will also be a 1800 mile round trip from northern michigan to memphis tn. not towing anything and probly oing to average 70 mph so we'll see...

Mine does best if I keep the rpm under 2000, that's about 68 mph in my truck