Sorry, this is a non-argument because you are trying to solve a non-existing problem.

The calculation used to determine range or cost when you have miles-per-gallon or km-per-liter is trivial and just as familiar as the liters-per-distance calculation when viewed in context.

My point is that if you actually LIVE in an environment where miles-per-gallon is the norm you develop familiarity with the numbers. You develop a sense of proportion. The calculations are not difficult because they are normal to you. To anyone transitioning back and forth between the two systems, well, there will have to be an adaptation period during which things will be uncomfortable until they are not.

Besides, people very rarely have to make these calculations today. My car tells me how many miles I have left in the tank based on the average historical fuel consumption since I've owned it. No math required. When I fill up, it updates that number.

Still, you very quickly learn that you get X number of miles with a full tank of gas. You just know that. You also learn you need to refill your tank N number of times in the course of a month on average due to your normal driving patterns. None of this requires much thought. And, if you are going on a long trip you generally know how far you can go on a single tank of gas and hopefully you've verified that there are gas stations along the route to top-off as you go (which in the US is generally the case).

As far as calculating the cost of a trip, again, if you live in miles-per-gallon land it is easy. Nobody goes into a crying frenzy screaming "Why, oh why don't we use liters per 100 km. This is so hard!". No, instead people have an estimate of their average miles-per-gallon or an accurate historical average from their car's information display system. They get the distance to their destination and divide. And, no, there's no need to divide 483.5 miles by 21.3 miles-per-gallon. That's insane. Nobody does that. Your goal is to get a sense of proportion of how much fuel you'll need. So, you divide 500 by 20 and you'll get a decent number. It won't be twice that many gallons nor half. There are plenty of gas stations along the route. No worries. And, if you need an accurate number for reimbursement purposes, well, keep the receipts.

So, again, I think you are trying to solve a non-existing problem.

Now, on the question of metric vs. imperial. Well, I detest the imperial system of units. I hate it. I use metric for engineering purposes. The world is metric. It is ridiculous that we haven't made the switch.

That said, I fully understand why. Unless you've traveled through the US it is hard to get a sense of proportion. This place is huge. The infrastructure is of unimaginable proportions. Going metric could very well take 100 years due to the sheer amount of work and cost involved. So, yeah, I get it.

There are other seemingly minor examples of this. We sell internationally so I am very aware of cultural and systemic differences. For example, most of the world would write one thousand dollars like this: $1.000,00. In the US it is written like this: $1,000.00. In the US 1/2/2015 means January 2nd, 2015. In the rest of the world it means February 1st, 2015. In the US we use AM and PM. In a good deal of the world it is a 24 hour clock (which makes far more sense).

There are a lot more examples of this. If we can't fix something as simple as what the comma and period mean when speaking about money or the order of the day and month on a date we are doomed to fail in shifting the US to the metric system.