Mazda's always had cool technology. They're the only carmaker that's steadily developed the compact, high-output Wankel rotary engine, for instance. And they're known for powerful, high-revving piston engines and slick-shifting gearboxes.

Then there's the green side of the brand, which already sells mostly small and relatively fuel-efficient cars. Not only will U.S. buyers get the 2011 Mazda Mazda2 subcompact soon, but the company is evaluating whether to offer its iStop start-stop system on some U.S. models.

2010 Mazda CX-7 s Grand Touring

2010 Mazda CX-7 s Grand Touring

Mazda SKY D diesel engine

Mazda SKY D diesel engine

Mazda SKY Drive transmission

Mazda SKY Drive transmission

What's so cool about iStop? Well, unlike so-called micro-hybrid systems--which restart the engine using a beefed-up 12-Volt battery and starter motor--Mazda's iStop switches off the engine with one piston slightly past the top of its compression stroke.

When the driver starts to lift off the brake, the iStop system sends power to the appropriate spark plug, the engine fires, and it resumes operation--all without involving the starter motor. Pretty ingenious, right?

Now the latest potential zoom-zoom technology is the company's line of diesels, which it offers in Europe--where new diesels take 50 percent of new-car sales due to much lower taxes on diesel fuel--but has never sold in the States.

Robert Davis, who is Mazca's senior vice-president for quality, research and development, told us last fall that the company believed its next generation of gasoline engines would be as fuel efficient as today's diesels.

And its next generation of diesels? Well, Davis said, they would match the gas mileage of hybrid-electric vehicles today, which means in the high 30s and low 40s in miles per gallon.

With gasoline prices well down from their $4-per-gallon high of two years ago, several Japanese carmakers who had planned to launch diesel engines in the States--among them Honda, Nissan, and Subaru--have postponed or canceled their plans.

Might Mazda be the first to join the Germans (Volkswagen, Mercedes-Benz, and now Audi and BMW) in offering high-mileage clean diesels in the U.S. market?

The company isn't committing, but its CX-7 crossover is a likely candidate. While it comes with a high-torque, 170-horsepower 2.2-liter turbodiesel in Europe, a U.S. diesel would likely come from Mazda's all-new Sky engine family, fitted with a direct-shift gearbox.

But we're aching to see what a sporty 2010 Mazda Mazda3 compact hatchback might be like if it were fitted with a 35-mpg-plus diesel engine that kept all of its zoom-zoom intact. What a competitor for the popular 2010 VW Golf TDI. Color us ... very interested.

[Road & Track]