There is an ever growing need for diesel technology to improve, which constantly puts pressure on diesel engine manufacturers. This is due to a combination of government pressure as well as the fact that diesel engines are behind the times, especially when compared to the highly efficient hybrid engines.
Many utility vehicles such as busses and trucks are still powered by diesel engines, and while they are modified to fulfil government requirements and emissions standards, they are all riding a fine line of being outright replaced by newer fuel technology.
The days when diesel fuel was significantly cheaper than gasoline have ended. Now it costs roughly the same, or more to fill the tank of a diesel vehicle. Not only this but the pump price of diesel is likely to rise, due to competition from other users of the fuel, such as commercial trucks, home heating oil, and industrial generators.