Are Diesel Engines More Efficient Than Gasoline Engines?

With the recent Volkswagen emissions measurement scandal, are diesel engines really more efficient than gasoline engines? 

By: Ringo Bones 

Ever since German engineer Rudolf Diesel patented his diesel engine, the industrial world was quick to embrace it with open arms given that your typical diesel engine burn about 25-percent less fuel in comparison to a gasoline engine of similar horsepower rating, not to mention that diesel fuel, as a byproduct of crude oil refinement, is around 4 to 5 times cheaper than gasoline when a barrel of crude oil produces 19 gallons of gasoline and 12 gallons of diesel fuel when it is refined. And given this “ energy utilization efficiency”, diesel engines by their very nature only produce a quarter of the carbon dioxide produced in a typical gasoline engine – which is now of paramount importance in our increasingly climate change conscious world. But sadly, diesel engines are inherently way dirtier than gasoline engines when it comes to oxides of nitrogen and particulate emissions. 

The row over whether diesel engines – as in diesel fueled cars and trucks – are really more environmentally friendly than their gasoline engine counterparts recently came to light in the form of the recent Volkswagen emissions measurement scandal where the famed German automaker was caught by the U.S. Environmental Protection Agency back in September 21, 2015 when Emissions Analytics, an internal combustion engine / automotive emissions testing lab recently uncovered that the latest models of diesel fueled Volkswagen cars sold in the United States employ a “cheating software” on its electronic engine management system that automatically reduces the engine’s power output and thus the resulting emissions output when it detect that the car is mounted on a tachometer – a device used to statically test the power output and combustion byproducts of cars under test. The Volkswagen “cheating software” allowed their late-model diesel cars to produce up to 40 times less oxides of nitrogen and particulates in a lab testing setting when compared to being actually driven on the road. 

Whether the “cheating” is deliberate or not, from a scientific viewpoint, diesel engines still produce less carbon dioxide – a potent greenhouse gas and the primary cause of the ongoing climate change – than their gasoline counterparts, but the oxides of nitrogen and particulates produced by diesel engines also have a deleterious effect on our environment and of human health. The oxides of nitrogen produced by diesel engines can promote the formation of smog and increases the acidity of rain and can also do nasty things to our lungs due to its corrosive nature. Particulates that are the byproduct of diesel combustion can increase anyone with a compromised immune system to catch pneumonia. Diesel engines may be more fuel efficient and produce less carbon dioxide than gasoline engines, but clean they are not.