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Although diesel cars are popular across Europe, Asia, and Australia, in the United States, their sale has been prohibited by five different states - New York, California, Vermont, Maine, and Massachusetts - due to concerns about the emissions they release. These concerns may be dated, however, especially in today's world of cleaner, quieter diesel engines.
It is a well known fact that diesel cars are more fuel efficient cars. A litre of diesel fuel fed into a diesel motor can easily outperform a litre of gasoline fed into a gasoline motor. The average diesel motor gets many more kilometres per litre than the average gasoline motor. Diesel motors also offer a much higher ratio of torque than gasoline motors of similar weight, meaning that they are able to haul much more cargo.
Although the average diesel motor tends to be priced higher than the average gasoline motor, it is usually still cheaper than the average hybrid motor even though it offers a similar style of fuel efficiency. Let's compare two similar Mercedes Benz vehicles, one with a diesel engine and the other with a gasoline engine, for a better idea about the differences between diesel cars and gasoline cars. The diesel powered E320 from Mercedes' 2007 lineup costs the tiniest fraction more (one fiftieth to be exact) than the gasoline powered E350, also made by Mercedes in 2007.
The diesel powered E320 features a 3.0 litre V6 engine with an incredible 388 pounds per foot of torque, which can kick in from only 1600 revolutions per minute. The gasoline powered E350, on the other hand, has a 3.5 litre V6 engine with only 258 pounds per foot of torque, which kicks in at a huge 2400 revolutions per minute. The E320 gets a full 11 kilometres per litre of diesel fuel when driving in the city and as much as 15 kilometres per litre for highway driving. The E350, on the other hand, only makes it to about eight kilometres per litre of gasoline fuel when driving in the city and only gets about 11 kilometres per litre when on the highway. This comes to an average of about four kilometres more per litre of fuel for the diesel model.
The reason most diesel cars are most efficient than their gasoline powered counterparts has to do with the combustion cycles of their engines. The combustion cycle of a gasoline engine involves fuel first being mixed with air. This mixture is then sucked into the cylinder where it is lit by one of the spark plugs.
In a diesel engine, this cycle is similar but different. With no fuel being involved at first, simple air is sucked into the cylinder by itself where it is compressed and held. The compression causes the air to heat up rapidly. Once the air is nice and hot, diesel fuel is finally injected into the cylinder to join the compressed and heated air. The heat causes the fuel to immediately combust.
Thanks to both the higher combustion temperatures and the higher compression ratios in the diesel engine, its fuel is used much more efficiently. Less fuel being used means greater fuel economy and less money spent when it comes time to refill the tank. Besides these ratios and temperatures involved, a litre of diesel fuel actually contains slightly more energy than a litre of gasoline fuel.
The larger amount of energy in the diesel fuel combined with the greater efficiency of the diesel motor together account for the better fuel economy in diesel cars. Today's diesel car also starts better in cold weather and comes with an array of modern vibration damping techniques in order to keep the notorious noise to a minimum.
