Cessna Citation Longitude Mach mode ?

[cantremember 27]

I'm getting to grips with the autopilot and autothrottle of the Cessna Citation Longitude.

One thing I can't figure out is the autothrottle with Flight level Change mode.
You can select either knots or mach. But if you choose mach, it doesn't reflect the mach speed on the airspeed ribbon,and it also doesn't keep a specific mach speed during the descend or climb, instead maintains amount of knots since last time you changed the knob.

EDIT: Also, I set the full tank sliders to 100% and did an IFR flight at FL450, but despite the 3k or so range, I didn't even make it across France before running out of fuel, anyone know if I'm missing something obvious that could have made the consumption very high?

Edited September 2, 2020 by cantremember