Kinda related...but not really... I drove a 08 duramax diesel w/allison on a 6.7 mile test drive today...trip computer said I used 1.3 gallons...I was in it a little

Oh yeah the best I got was a solid 10MPG 525 cube Stage V heads and intake, 245@ and about 550 lift. 354 Dana in E-body.
Curt