One of the nice things about cars from the last five years is that they keep track of fuel usage and time that the engine runs, and they let the user easily access the information. Based on my last two months of driving, I've driven at an average of 64 km/h, which surprises me. I thought that the amount of idling to warm the car would have brought this down somewhat.
Fuel economy didn't surprise me. We get an average of 5.8l/100km, which fits in nicely with the measured amount that our Fiesta should be getting for highway driving. I'd assume this will probably go up after we move in to Edmonton.
A lot of people measure their car's efficiency by cost/km. I think if one was going to charge for their driving this makes sense, but it's a difficult method to visualize. A simpler method would be cost per hour. Our car gets 5.8l/100km*64km/hour, or 3.71 liters per hour. Looking at our current local average gas prices, that's $3.33 per hour of driving. I can't complain there.