One of the most common, and most tragic, misconceptions about diesel engines is that they are dirty—and they burn dirty. The image of a giant semi-truck barreling down the highway, belching out thick black smoke is burned into the populace’s collective mind. New restrictions and regulations set by the government led to the cleaning of diesel engines. Now, they’re cleaner and more fuel-efficient than gasoline engines. Diesel engines are popular because they can run on alternative fuels, not just diesel fuel. In fact, when Rudolph Diesel unveiled his invention at the 1900 World’s Fair, it was powered by peanut oil. So, what fuels can a diesel engine run on?
The first, and most obvious, fuel source for the engine is diesel fuel. After Mr. Diesel introduced his engine, the petroleum industry cashed in by using a byproduct of petroleum distillation to power the engine. They called it diesel fuel in a brilliant bit of marketing. Today, the fuel is available at most gas stations across the country and used in various vehicles. Diesel fuel is more stable and less combustible than gasoline. In fact, if you tossed a lit match into a puddle of diesel, it would go out. If you did the same with gasoline, the match wouldn’t hit the ground before the gas ignited.
Kerosene is the brother of diesel fuel. It is called #1 diesel fuel oil and diesel is called #2 diesel fuel oil. The similarities are so close that some people use #1 interchangeably with #2. Kerosene is lighter and therefore carries less energy than diesel fuel. It also burns drier and can cause problems for fuel pumps and rings within the cylinders. The best way to utilize kerosene is to mix it with diesel, because it will cut down on the emissions and keep the diesel from gelling in the cold winter months.
Because of how a diesel engine works, it only needs something in the chamber that will burn—it doesn’t have to be petroleum-based. Biodiesel is engineered so that it has the same physical properties as diesel fuel. It has a similar viscosity and weight so that it behaves the same way. But it is made of vegetable oils and animal fats. It goes through a refining process to remove anything that might damage the engine, but it’s completely free of fossil fuels.
Diesel engines will run on straight vegetable oils (SVO). That includes just about anything you can think of—peanut oil, sunflower oil, corn oil, animal fats, and so on. But you can’t just dump it in the tank. The oils need refining so they’ll flow from the tank to the engine easily and not clog up fuel injectors and cylinders. SVO is thicker than diesel fuel and biodiesel, so its viscosity must be brought to a similar level for it to work.