We won't see it here, but diesel fans everywhere are eagerly waiting for the world's smallest, cheapest four-seat diesel passenger car to be launched later this year in India.

The Tata Nano Diesel may get as much as 70 miles per gallon or more, making it the most efficient four-seat diesel vehicle on the planet.

The Indian new-car market is shifting rapidly to diesel vehicles, as increased taxes on gasoline give more expensive diesels a better payoff.

And Tata, which has seen disappointing sales of its Nano minicar, developed to be the world's least expensive car, knows it needs a diesel model to build out its range.

Thus far, we have seen only rumors and spy shots from Indian auto sites like IndianCarsBikes and IndianAutosBlog--but together, they add up to an intriguing picture (with multiple images neatly assembled in a slideshow).

The diesel Nano will have a 0.8-liter two-cylinder diesel, codeveloped by the German firm Bosch, with the world's smallest Honeywell turbocharger. It puts out approximately 35 horsepower and 52 ft-lb of torque.

In a car that weighs only 1,500 pounds, that will be enough--and, it's targeted to deliver fuel efficiency of 40 kilometers per liter, or 94 miles per gallon.

2012 Tata Nano

2012 Tata Nano

That's on a specifically Indian test cycle, so a more likely figure on U.S. test cycles might be closer to 70 miles per gallon.

Still, that would make the tiny turbodiesel Tata more fuel efficient than anything sold in the U.S. without a plug today (and most likely slower as well).

Let's be clear: The Tata Nano itself will never be sold in the U.S., let alone its diesel variant.

It wasn't designed to be Federalized, an exercise that costs $100 million or more to get a car to pass stringent U.S. crash-safety and emissions standards.

Even if it had been, the prospect of a tiny, low-cost minicar joining Jaguars and Land Rovers in showrooms (Tata owns Jaguar Land Rover) seems like a gigantic stretch--especially given the low volumes of minicars sold in the States.

But the diesel Nano does point to an immutable truth for the cars of the next decade: They're going to get far better gas mileage by using smaller, more efficient engines.

Meanwhile, minicar and diesel fans together can dream about driving the world's littlest four-seat diesel.


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