Difference between Gasoline and Diesel
Gasoline and diesel are both widely available fuel choices for automobiles. How do they differ and which one is better? The answers to these questions may surprise you.
Both gasoline and diesel are produced from refining of crude oil. The crude is heated and when each of these oils reaches its boiling point, it turns to vapor. The segregated vapor can be condensed into the individual product. These oils with specific characteristics are referred to as fractions of the original crude oil.
Fuels are measured by their energy density (BTU value). In general, gasoline has about 85% of the energy density of diesel. Visually, gasoline is much lighter and clearer. Diesel looks heavier and more oily. Gasoline is one of the lightest fractions to come out of the refining process because it has one of the lowest boiling points.
Gasoline and diesel engines work differently as well. A gasoline engine takes air and fuel and compresses them together, then sparks the mixture to cause an explosion which moves the piston and creates power. A diesel engine injects fuel into already compressed air which causes a spontaneous explosion because the compression has already heated the air.
A properly performing diesel engine gets better gas mileage than a comparable gasoline engine. The combination of higher energy density fuel and the higher compression ratio of a diesel engine yields more miles per gallon. A high compression ratio means the engine is able to extract more power from the explosion of the fuel inside the cylinder.
In order to stand up to the higher compression levels, diesel engines are heavier and more expensive to manufacture. However, they have a substantially longer operating life than gasoline engines. Diesels routinely run for hundreds of thousands of miles. This is one of the reasons they are so prevalent in commercial trucks, which are constantly on the road. There may be a higher cost upfront, but the lifespan is often twice that of a gasoline engine.
Diesel has had a reputation for being a dirty fuel, but modern engines are changing that. Computerized engine optimization combined with emission controls yields much cleaner-operating diesels. Soot is also a challenge that is being handled with filters and catalytic converters. As of December 1, 2010, all highway fuel sellers in the U.S. are required to sell ultra low sulfur diesel (ULSD), further reducing the emissions.
The popularity of diesel in Europe is far greater than in the U.S. With gasoline prices exceeding the equivalent of six dollars per gallon, Europeans appreciate the fuel-efficiency and longevity of diesel engines and the lower cost of diesel fuel.
With all the concern for the environmental impact of burning any kind of fossil fuels, deciding to run a car on either gasoline or diesel may not improve the air quality. But until more alternatives are available, it might be worth giving diesel a second look.
