Fueling infrastructure isn't something automakers traditionally had to think about much.

For more than a century, oil refiners and distributors have built and run a network of gasoline stations to fuel the world's billion-plus vehicles.

Many of those stations in the U.S. carry diesel fuel, though not all.

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But as more diesel passenger vehicles enter the market, availability of diesel fuel is increasing even as the overall number of gas stations falls.

'Diesel fuel only' caution on Audi Q7 TDI

'Diesel fuel only' caution on Audi Q7 TDI

Historically, about half of U.S. gas stations have offered diesel fuel--generally in urban areas where diesel delivery trucks operate, and rural areas where farm equipment is often fueled by diesel.

That number has now risen to 55 percent in North America, according to Integer Research data from last May provided by the Diesel Technology Forum.

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Regionally, Canada has the highest proportion of diesel availability--it's found at 69 percent of stations--and the U.S. East Coast is lowest, at 51 percent.

In addition, diesel is increasingly being integrated into the main pump islands--rather than locating diesel pumps elsewhere on the gas station property.

Percent of U.S. and Canadian gas stations selling diesel fuel as of May 2014

Percent of U.S. and Canadian gas stations selling diesel fuel as of May 2014

Diesel fuel located outside the main pump area meant that Mom may have had to drive her car out back and fuel up next to semis or tractors.

And that discouraged at least some drivers from pursuing diesel vehicles.

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Steve Hansen of the Diesel Technology Forum notes there are two forces driving the rise in diesel availability and its migration into main pump ranks.

First, stronger regulation of underground fuel storage tanks at gas stations over the last 15 years has forced gas stations not only to install new, tougher tanks, but to reconfigure them.

Diesel fuel pump

Diesel fuel pump

Two of the traditional three tanks are now generally used for 87- and 91-octane fuel ("Regular" and "Premium"), while new blender pumps create mid-grade 89-octane fuel by combining the two.

That frees up the third tank, and some stations are choosing to use it to sell diesel fuel.

Second, Hansen says, diesel fuel will be more profitable to sell in the coming years than will gasoline--offering a powerful economic incentive for stations to convert.

That's because demand for diesel will grow even as demand for gasoline falls.

Also, because gasoline is ubiquitous, it is still more subject to price wars than diesel will be as convenience stores use gasoline as a loss leader to bring in customers who will then buy more profitable cigarettes, lottery tickets, and salty snack foods.

2014 Ram 1500 EcoDiesel, Bear Mountain, May 2014

2014 Ram 1500 EcoDiesel, Bear Mountain, May 2014

As proponents of alternative fuels--natural gas and hydrogen among them--have learned, building fuel distribution infrastructure is expensive, lengthy, and complicated.

It's one of the reasons that a number of analysts suggest gasoline, diesel fuel, and electricity will remain the primary energy sources for most vehicles: All have well-established distribution networks.

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The number of North American outlets selling diesel fuel is likely to increase, albeit slowly, making the fuel more readily available to a wider number of drivers.

And that rise will likely parallel the slow growth in sales of diesel light trucks, especially pickups and SUVs, and perhaps even passenger sedans.

The result will be more fuel-efficient diesels joining increasingly fuel-efficient gasoline vehicles on North American roads.


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