Asking, “Why do Europeans drive diesel cars?” is another way of asking, “Why don’t Americans drive diesel passenger vehicles?” There are probably a number of reasons why Americans — at least those who live in the United States — don’t drive diesel cars. 

One reason is the fact that diesel engines are, mistakenly, associated with pollution. Misinformed people often think diesel engines produce more pollution than gasoline vehicles. That is not true. The black smoke associated with the diesel engines of the past is no longer an issue. And, even when diesel engines did produce black smoke, diesel engines still produced fewer emissions than petrol engines. 

Another reason people in the U.S. tend not to drive diesel passenger engines was that — again, in the past — diesel engines were slow with respect to acceleration. Diesel engines have considerably more torque and power at low rpm. But traditionally, diesel engines had lower top-end speeds and much less quickness off the starting line. 

Why Europeans drive diesel cars has very little to do with why people in the U.S. don’t. 

So, why do Europeans Drive Diesel Cars Then?

Europeans drive diesel cars, primarily, for three reasons. First, diesel engines are more fuel efficient, much more fuel efficient. That is to say, diesel engines get much better “gas” mileage than their gasoline counterparts. Another reason Europeans seem partial to diesel passenger vehicles is that diesel engines last much longer than gasoline engines, A diesel engine will last two and three times as long as a gasoline engine. 

Better gas mileage and longer lasting engines are enough to convince Europeans that diesel engines are better than gasoline engines. But, contrary to popular belief — diesel engines pollute less than gasoline engines. Diesel engines especially pollute less than gasoline engines that require “premium” gas. Europeans drive cars with diesel-powered engines because they are cleaner, more efficient, and have greater longevity than gasoline engines.

Why Diesel Engines Pollute Less

Gasoline engines pollute less than gasoline engines because diesel has a higher fuel density than gasoline. Fuel density is the product of the length and structure of the hydrocarbon molecules that make up a fuel. The average hydrocarbon in gasoline has between 5 and 12 carbon atoms. The hydrocarbons in diesel — the molecules in diesel that combust and burn and create energy — average between 8 and 21 carbon atoms. In carbon-based fuels, the larger the number of carbon atoms in a hydrocarbon, the greater the density. 

Fuel density in fossil fuels determines two things. First, fuel density determines the distance an engine will travel on a gallon or liter. And, fuel density determines how much pollution a combustion engine per mile. 

Pollution is a vague and disputed concept. What pollution is, exactly, is up for debate. But, the most common measure of pollution — at least with respect to combustion engines — is carbon emissions. There are two types of carbon emissions associated with combustion engines: carbon dioxide (CO2) and carbon monoxide (CO). The amount and types of carbon emissions a combustion engine produces are its carbon footprint. 

The carbon footprint of a diesel engine is less than that of a gasoline-powered engine. For one, a diesel engine produces almost zero carbon monoxide, only trace amounts. And two, diesel engines produce less carbon dioxide. 

Carbon Dioxide Emissions Per Gallon vs Per Mile

Proponents of gasoline point out the fact that per gallon, gasoline engines pollute less than diesel engines. But, measuring emissions per gallon ignores fuel efficiency. Measuring the emissions of a fossil fuel ignores the “gas” mileage of engines. 

It is true. Diesel engines produce more carbon dioxide per gallon than gasoline engines. But, saying gasoline engines produce less carbon dioxide than diesel engines — because they produce less per gallon — is misleading. Diesel produces roughly 22.38 pounds of CO2 per gallon. Gasoline only produces about 19.64 pounds. That is a difference of 13.3 percent. Per gallon, diesel produces about 13 percent more CO2 than gasoline. 

Diesel engines are between 25 and 35 percent more efficient than gasoline engines. That means — per mile — gasoline engines produce between 12 and 22 percent more CO2 than diesel engines. 

Emissions per Mile

Emissions over distance is a much more accurate means of determining the carbon footprint of a fuel than measuring emissions per unit of volume. The reason being, travel is measured in distance. The distance between the two locations does not change. Distance is constant. But, the number of gallons of fuel required to travel between two locations varies depending on the vehicle being driven. So, while a gallon of diesel produces more CO2 than a gallon of gasoline does, on a trip of a given distance, a gasoline produces more CO2 emissions. 

That is to say, the person who drives a diesel-powered car to work every day produces fewer CO2 emissions than the person driving an equal distance every day in a gasoline-powered car. 

Better fuel efficiency and lower emissions are only two of the reasons Europeans drive diesel-powered cars. The life of a diesel engine, compared to that of a gasoline engine, is the third reason. 

Longevity of Diesel Engines

Diesel engines last two to three times as long as gasoline-powered engines. The reason why is simple. Diesel engines are heavier and sturdier than gasoline engines. Gasoline engines are, for lack of a better word, simply built cheaper than diesel engines. 

Diesel engines are built more robustly than gasoline engines out of necessity. Diesel engines are compression-fired engines as opposed to spark-fired engines. Rather than a spark from a spark plug igniting diesel, the piston in a compression-fired engine compresses the diesel in the engine cylinder until it auto-ignites. Because of the pressure necessary to auto combust diesel, the cylinder walls of a diesel engine must be extremely thick. The entire engine, in fact, must be considerably heavier than a gasoline engine in fact. Because diesel engines are built so robustly, they last longer than gasoline engines.

Simply, Europeans drive diesel cars because they like fuel efficiency; they like cars with long engine life; and Europeans like polluting less more than Americans do.