Honda and Acura have been contemplating bringing diesel engines to the U.S. for some time, but in late October word broke that the engines had been delayed. At the time the reason had been thought to be trouble with 50-state emissions certification, but now the company has revealed the real issue is with the high price of diesel relative to gasoline in the U.S. and materials prices.

Whether Honda's move presages similar decisions by other companies is anybody's guess, but the numbers don't lie, and diesel is simply too expensive to justify, even with the fuel savings.

"Right now we are re-evaluating, due to trends in gasoline and diesel prices, and the price of raw materials we use in the exhaust clean-up system," said David Iida, a Honda spokesman.

The fuel itself costs 40-50% more than gasoline, reports The Detroit Free Press, but the cars are only 20-40% more efficient, and they command a premium of about $1,500 over their non-diesel counterparts. Acura had previously been planning on bringing a 44mpg diesel engine to its Acura TSX (known outside the U.S. as the Honda Accord Euro).