If fossil fuel were absolutely free of impurities, you wouldn’t have to worry about soot in the engine. Gasoline has fewer impurities than diesel, but diesel fuel is more commonly used in industrial applications due to its energy potential. According to the Alternative Fuels Data Center, a gallon of diesel has 13 percent more energy than a gallon of gasoline and, as such, yields more torque.
Despite being more than $0.20 costlier than gasoline—as per current fuel price data—diesel fuel offers better fuel economy due to its higher energy potential. A massive cargo hauler can, for instance, travel farther for the same amount of fuel a car uses. Expect fuel economy for diesel engines to rise with stricter federal regulations in the coming years.
Even if impurities in fuel become a thing of the past, fuel filters will still face their other enemy: air. Even in a pre-climate change environment, air still contains lots of impurities that can affect engine performance. Remember that the engine requires the ideal mixture of fuel and air to initiate combustion. A dirty filter will cut the amount of fuel entering the chamber.
It is clear, therefore, that filter replacement should still be part of any maintenance routine. With clean and efficient filters, it is easier to keep the air cleaner.