I, like most, have the extended fuel tank. While there is a comment in the manual, the reading is not accurate and the needle does not move past full until after about 150 miles. Brought it to the dealer and they recalibrated it, but no difference. Anyone else having this issue?

 

This is normal.

The needle doesn't really move until about at least 5 gallons are gone.

 

The other funny thing, is that the miles to empty goes up as you drive when you have a full tank. The extended tank has the extra capacity in the bottom of the tank, where the AWD system would be in the C4S or turbo that the tub is for.

 

Normal.
Basically it sits on full until the level reaches that of the standard tank, then it starts to drop. Very fast if on track!