I feel the same.
I would've liked either one of those two: bigger tank, or better mileage. For now, this is my second gas fill up and I'm doing about 400 km with a full tank, so around 12.5 liters per 100 km.
Lucky for me, the gas station is just around the corner of my street.
Also, I know the truck is brand new and I'm always driving it as soon as I have the chance to do so. I'll get used to it a bit more and change my driving habits a bit also and in the end, get much closer to what is advertised about the fuel consumption.
I'm not that far from it either, about 15% or so higher than the advertised city driving fuel consumption.
Anyway, it is far less than my Chevrolet Venture's V6 that was eating about 15 or 16 liters per 100 km.