"how far can I drive for this amount of $" is a question I've only heard a few times. But I do often hear "how far can I drive on a tank" or "how far can I drive on my remaining amount of fuel".

Perhaps the disconnect we see in this comment thread is between people who do almost entirely city driving and people who drive long distances. If you only ever drive a few miles at a time, you don't really care what sort of distance you can manage on a tank, you just care how much it's going to cost you to go to work every day (you'll probably convert the fuel/distance ratio into a money/time ratio.) If you spend a lot of time driving across central Kansas, how often you have to stop for gas becomes a more significant consideration (you'll probably convert distance/fuel into stops/time.)

How often you stop for gas is surely better covered by a "range" measurement for the car? Maybe it's different in the states, but all the cars I've ever been in show your remaining fuel as a fraction of a tank. In that case, volume of fuel is completely irrelevant, so MPG vs liters/100km has not place. e.g. My tank takes me 400 miles => I have half a tank left => I can go another 200 miles ...is exactly equivalent to... My tank takes me 600 km => I have half a tank left => I can go another 300 km

(For the purposes of this post, 1 mile = 1500m. If the size of a gallon changes with locale, why not a mile? :-p )

> Perhaps the disconnect we see in this comment thread is between people who do almost entirely city driving and people who drive long distances.

That's an interesting thought, and it probably has more than a grain of truth.

Maybe. I tend to live in rural areas so maybe that's a factor.

But I was more thinking of this:

"We have a vacation budget of X for a weekend trip. We don't want to spend more than Y for gas. What options do we have?"