The 2014 Ram 1500 EcoDiesel pickup hasn't quite reached dealers yet, but its high fuel-economy rating is already making an impression on truck buyers.

Ram says it received more than 8,000 orders for the EcoDiesel in just three days, completely filling the initial allocation planned for the diesel half-ton pickup.

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A significant number of those orders--more than twice the corporate average, Ram says--are from individual customers, rather than dealers building stock.

And those customers placed their orders even though they most likely haven't even test-driven the new trucks.

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The flurry of buyer interest comes shortly after the announcement of an EPA fuel-economy rating of 23 mpg combined for rear-wheel drive models.

2014 Ram 1500 EcoDiesel

2014 Ram 1500 EcoDiesel

That corresponds to a city rating of 20 mpg, and a highway rating of 28 mpg--which Ram says is the highest for any full-size pickup truck ever tested by the EPA.

Four-wheel drive models are rated at 22 mpg combined (19 mpg city, 27 mpg highway).

The 3.0-liter EcoDiesel V-6 is the same one used in the Jeep Grand Cherokee EcoDiesel, and is the only diesel engine available in a half-ton truck this year.

The engine produces 240 horsepower and 420 pound-feet of torque. An eight-speed automatic is the only transmission option.

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Like the rest of the Ram 1500 pickup range, the EcoDiesel is equipped with other fuel-saving features, including active grille shutters, aerodynamic under-body panels, and an engine start-stop system.

Production of the 2014 Ram 1500 EcoDiesel began this month, but trucks won't be delivered until March, following a build-quality review process that is standard procedure for new models.

Trucks ordered by individual customers will get priority over those ordered by dealers so those buyers should receive their vehicles first.

Ram will begin taking the next batch of orders in early March.

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