While walking the streets of Europe, you notice that their cars are somewhat different from what we drive in the U.S. You may have never heard of some of these manufacturers, or never seen some of these car body-types. But you will notice that something is missing: hybrids. Instead you will notice an overwhelming number of clean diesel cars. These cars have replaced the old, sputtering diesel with a new breed, called TDI (turbocharged direct injection, made by VW group) or BLUETEC (a Mercedes-Benz product). Diesel engines are not just for trucks anymore. The TDI engine won the Le Mans 24hr endurance race 5 times between 2006-2011. Their success and growing popularity is due to their increased efficiency, power output, and torque compared to a conventional gas engine, as well as reduced emissions. But clean diesel rivals hybrids in the competition to be the most eco-friendly. The TDI engine was featured in the green car of the year 2009 & 2010. The VW 1.2 TDI 3liter engine won best fuel economy over the toyota prius. But you must consider something that the estimated mpg doesn't tell you: the environmental impact of manufacturing. The batteries in a prius come from a nickel mine in Ontario, where they are mined using a very abrasive process (so bad NASA tests lunar rovers in now-desolate area). Once removed from the earth, the nickel is loaded onto a massive cargo ship and taken to a refinery in europe, then to China, and to the toyota plant in Japan. Once the car is assembled, it is once again loaded onto a ship and brought back to the U.S. After all that, there is no way it can be better for the environment than the cars we are already driving. Instead of trying to use a technology that isn't fully developed, Americans should revert to our old friend, the diesel.