From the trips out west through the mountains it turns out that I'm picking up up to 12% better economy due to the density altitude effects.
Since I'm never asking for any where near full power,it's easy for the EFI to maintain whatever air/fuel ratio it's looking for without going rich.
The thinner air cuts the drag down as if the Cd were actually lower than it is.
I do pay a penalty with grades but once into a relatively level stretch she cruises effortlessly.
The 6th-gear would be helpful.
You're rig may be experiencing a similar effect.
Nice numbers for a gas-burner!
