I do the math.

I read an article recently about the astonishing inefficiency of the internal combustion engine. Apparently, only 16% of the energy it consumes ends up moving it forward (or backward), which is the whole point of the car after all.

Not entirely believing this, I checked around and kept coming up with similar numbers -- the motor car engine is only about 20% mechanically efficient, the rest of its energy being lost to heat, water heating, motor friction, and noise. The original article included idling, so its lower number is quite reasonable.

And it makes tea, too.

Now, no engine is ever going to get anywhere near 100%. (Want to know the most efficient engine currently measured? Human power. The bicycle.) Perhaps if we'd stuck to refining the steam-powered tricycle that was built in 1769, we'd be in a better place by now. But that pesky Karl Benz shoved a gasoline engine into his 1885 auto, and the rest is oil, and the odd bedfellows it's brought us over the years.

(Proving that the key to success is to get into the balloon first and then devote all your resources to not budging. Incumbency always has the edge, even when common sense is howling for change. Ask the oil industry, the car industry, the tobacco industry, the music business, etc., and all those re-election-seeking fifth-term politicians they buy.)

Anyway, I thought I'd see where the numbers led. Not surprisingly, I got some wildly different estimates of energy consumption, depending on the interests of those doing the estimating, but I'm happy with this as a rough first draft.

I'll try to keep this simple. First, US oil consumption in 2010 was 18,686,000 barrels a day. The good news is, that's a continued decline from a peak in 2007. (Just for perspective, 4.9 million barrels leaked from the Deepwater Horizon spill over three months, which is the amount we consume as a nation in about six hours.)

Transportation in the US uses roughly 70% of the oil we consume. This seems to be a widely agreed figure -- it's basically the percentage of petroleum that's refined into gasoline, diesel, and jet fuel.

The hard part is separating out how much of that goes to roads, since diesel also fuels our long-distance trains. But I found a reasonable breakdown of transportation energy consumption that allotted 30% to light trucks (presumably less efficient users of gasoline), 28% to private cars and motorcycles, and 19% (mainly diesel*) to big trucks and buses. So 77% of the oil used for transportation is consumed on our highways. (This was on an educational website for kids, so it must be right.)

Okay, we multiply 18,686,000 barrels by 70%, then by 77%, and then by 80%, which represents the energy lost by the internal combustion engine. The answer comes to about eight million barrels. Give or take a gallon.

That's the amount of oil that ends up wasted on America's roads every day. Not just consumed -- wasted. Because we committed ourselves and our infrastructure to gasoline cars over a century ago. (That's 43% of our domestic consumption, if you're keeping track.) If we'd kept on studying and improving, say, battery technology or steam power during that time, instead of playing catch-up now, who knows what options we'd have today?

Want some perspective?

That wastage on America's roads is about 11% of the world's total oil production. One barrel in every nine. To heat your engine so much -- and so unnecessarily -- that you need a cooling system under the hood to keep it from exploding.

It's 90% of Saudi Arabia's oil production. It's just about equal to the combined oil production of Iraq, Iran, and Libya.

And it's more than our own domestic oil production.

Now, the US exports about a quarter of its oil, mostly to Mexico.** So just to keep our cars and trucks unnecessarily hot and noisy, we not only have to use up every gallon of our oil that we keep for ourselves, we also have to throw in pretty well everything we import from our largest supplier, which is our neighbor Canada.

From the nation whose car industry thought the Hummer was a neat response to a succession of oil shortages.

*Diesel represents about 28% of petroleum usage, so this seems to suggest twice as much diesel is consumed by long-distance trucking as by rail freight. Diesel engines are about 25% more efficient than engines powered by gasoline, although they still use internal combustion. I didn't allow for this in the calculation, but on the other hand I didn't include the idling factor either. Nor did I allow for the energy required to refine the petroleum into gas and diesel and its other products. Nor the oil used in our efforts to deal with pollution, or to maintain our car-oriented infrastructure -- where do you think that bitumen comes from? Nor all the completely unnecessary trips we make with our 20% forward motion, when the bicycle will do just as well.

**We also import about the same amount from Mexico. Go figure. (I know, I know -- there's oil and then there's oil. And it could vary with the seasons. I mean, it's not as if this 150-million-year-old substance keeps.)