I went to Buffalo last weekend in my car. I had 3/4 tank of gas when I started my trip. I kept the cruise around 110-115km/h all the way to the Whirlpool bridge to get into Niagara Falls, NY and my gauge only dropped down to just above 1/2 tank (so basically I burned a 1/4 tank driving there).

Once in the states and doing city driving, some stop and go, some cruising but then having to stop when traffic signals would change as I neared them sucked the rest of my gas to just below 1/4 tank. I did have to do a splash and go somewhere just outside Oakville before getting home. On my way home is usually where I'm a little bit more aggressive with my speeds therefore I use more fuel.

You can do your trip to Hamilton to see how your car does but if you start driving around the city and stuff what decent mileage you might get driving to H on the highway will probably get wiped out. You probably need to be on the highway longer to really gauge what your car could do when conditions are favorable.

On the gas light thing, again I don't think your light should come on with 14L or so of gas in the tank still. I just got fuel this morning my gauge was just above the E line and my light still hasn't come on (my display still showed I could go 30kms before my light will come on and my display shows "----" for distance to empty setting). On the 07 car it was the same thing light would come on with needle touching the E line and add another 70kms of distance or so before the car ran out of gas.