I am not certain it doesn't use the electric motor when towing. I have read somewhere that it does aid the gas motor when towing to increase hp and torque. I will only make sense that it does. I just don't think that it runs the truck on electric only if you are in tow mode.
As far as using the electric when towing, to increase gas mileage, I am still researching. If you put the vehicle in normal or eco mode when towing, it does go to electric on flats or downhills. I am just not sure if this is good for the truck.
Ecoboost was an option. I did research it but the Powerboost was a better appeal with 24mpg and more power and torque. It is also very very quiet.
I have to admit that I was surprised by the 30.6 gallon tank. I read everywhere the Max tow package came with it and it was only after I bought it that I read the footprint on the gas tank. I wish they had been more clear about this exception up front. Needless to say I was very disappointed. I guess they had to dump weight somewhere.
The truck is a great daily driver. I was just expecting better mileage when towing. Hopefully, things get better as the engine is broken in.
Mike