You can save a lot of money by improving the fuel economy of larger and thirstier vehicles, especially if they cover lots of miles each year.

That's why business owners are usually considered to be more rational vehicle buyers than retail customers: The fleet vehicles often consume twice the fuel or more of an average family vehicle.

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Yet for a long time, even as hybrids grew to 3 percent of the U.S. market and corporate average fuel economy standards took effect for 2012 vehicles, one segment persisted with ancient, thirsty vehicles.

That would be the full-size van market, split among "white vans" for tradesmen and windowed "church vans" for carrying up to 15 passengers.

2015 Chevrolet City Express van, 2014 Chicago Auto Show

2015 Chevrolet City Express van, 2014 Chicago Auto Show

Now, each of the three U.S. makers offers a European-style compact commercial van for sale in the U.S. And so does Nissan.

And, according to industry trade journal Ward's Auto, their sales are steadily increasing.

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The first smaller van was the first-generation Ford Transit Connect, launched in the U.S. for the 2010 model year.

The 2014 Transit Connect was an all-new design, replacing one that dated back to 2002 (the year it went on sale in Europe).

The new Transit Connect is a global vehicle, sold in dozens of countries around the world.

2015 Ram Promaster City

2015 Ram Promaster City

Similarly, the 2015 Ram ProMaster City can be seen on the streets of Europe and elswhere--although there it's known as the Fiat Doblo.

It replaces the Ram Tradesman, a windowless version of the Chrysler Town & Country minivan. But the new ProMaster City has a higher roof, side-opening rear "church doors," and other design features intended specifically for business use.

For the 2015 model year, Chevrolet now offers the City Express, a rebadged Nissan NV200 almost identical to the one Nissan dealers sell on their own lots.

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Both Ford and Chrysler have replaced their ancient full-size vans: The full-size Ford Transit replace the E-Series (formerly known as the Econoline).

The full-size Ram ProMaster replaces the old Dodge vans, which had the distinction of the "oldest doors" in the business, using elements of a vehicle that first went on sale in 1970.

Chevrolet thus far is sticking with its Express older full-size van, now offered largely with a 6.2-liter V-8 engine.

2014 Chevrolet Express 2500 Cargo Van

2014 Chevrolet Express 2500 Cargo Van

It is rated at 12 mpg combined, while the City Express comes in at more than double that: 25 mpg combined.

But the smaller vans are growing quickly, Ward's says, and suit lighter-duty businesses--especially those making urban deliveries--just fine.

Some dealers report steady demand as more businesses become aware of the new vehicles.

More than 43,000 Ford Transit Connects were sold last year, and the total small-van segment could go as high as

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