Comment Re:MPG testing - just to add (Score 1) 238
L/100km might contain the same information, but using distance as the domain is preferred. This is far more useful as people don't drive to burn fuel, they drive to travel. Distance is the important variable so fuel mileage should be with respect to distance. It makes comparing given fuel economy ratings easier as it better correlates with the amount of fuel you will use / cost of driving.
For example, consider the following fuel economy ratings: 4L/100km, 6L/100km, and 8L/100km. For a given distance, it is obvious that the most fuel efficient vehicle will be 1/2 the cost of the least efficient vehicle. The cost of third vehicle being is the average of the two other vehicles - or in the middle.
Now in mpg, those numbers are: 58.8mpg, 39.4mpg, 29.4mpg. Notice the 39.4mpg vehicle will cost the average of the 58.8mpg and 29.4mpg vehicles - but this is not apparent from looking at the numbers. It is because the numbers are represented using the wrong domain. Sure the information is there, it just is not represented in the most useful format.