Back in the days of $4-per-gallon fuel prices, diesel cars became the clamor of carmakers looking for a quick way to boost the fuel economy of their vehicles. Ford was one of the carmakers to jump on the diesel bandwagon, announcing plans to introduce a new 4.4L V8 diesel engine for the F-150 pickup truck as early as next year.

Now that petrol prices have fallen down to their pre-spike levels and is once again cheaper than diesel, it doesn't make economic sense for Ford to introduce a new diesel engine for the F-150 and thus plans for the oil-burning truck have been delayed. Ford is being hesitant about when the new engine might be introduced, but for now there has been no date pencilled as revealed by the carmaker’s American chief Mark Fields during a recent interview with Automotive News.

Despite Fields' comments that there is no definite date for when the engine will be brought into the F-150, an anonymous source from Ford revealed that the F-150's proposed diesel engine has been delayed until at least 2013. After this point, there is still no certainty it will be offered as an option as there is no business case for the engine if fuel prices remain at their current levels.

The new 4.4L diesel V8 engine under consideration for the F-150 improves significantly on the current petrol engine currently on offer. Initial tests have shown that the smaller diesel engine produces more power and torque than the 5.4L petrol V8, but still cuts fuel consumption and emissions significantly. Despite these qualities, diesel prices are the real barrier for Ford in the engine's introduction and until petrol prices rise or diesel prices fall we likely won't hear much about this engine.