As a Canuck, I find L/100km is the easiest way to compare fuel economy between countries. Around here we see vehicle advertised with MPG, MPIG, L/100km and km/G. (That last one really irritates me as it's intended to confuse people.) I guess L/100km is also easy for me to convert into $/day as my weekday commute is 110km.
110km @ 7.4L/100km @ $1.30/L ~= $10.50.
$/km (or mile) is the best comparison but it fluctuates too much based on the day (or hour) and location. Not something that can be published easily.
On the topic of fuel consumption ratings, in addition to "city" and "highway" I'd really like to see ratings like:
- 7.0L/100km @ 100km/h
- 10.0L/100km @ 120km/h
Actually, get rid of "highway" ratings and just list what the consumption is at various "typical" highway speeds.