Well, over time your engine's fuel pump and injectors get dirty. This is a gradual, hard-to-notice process that reduces both your car's engine performance and its fuel economy. This is because standard Diesel is not designed to reduced wear, extend the life of your engine or improve your driving experience - it is simply there to get your car from A to B. The result? Even the smallest amount of dirt on your car's critical engine parts will increase its fuel consumption, reduce its engine performance, and make it a less-smooth drive.