For the most part, the most fuel efficient diesel cars are from Europe. There is not as large a market in the United States for diesel cars, as many people think of them as loud and dirty compared to gasoline. That is changing with technologies that now make diesel cleaner and quieter. Also, in Europe there are fewer taxes on diesel which makes it much cheaper than it is in the states. Diesel has some advantages over gas, such as greater fuel economy, higher resale values for cars with diesel engines, and overall longer lasting cars. Here are some of the most fuel efficient diesel cars out on the market.
Volkswagen Jetta TDI
At a base price of $22,000, the Volkswagen Jetta TDI offers the best diesel fuel economy on the list. It gets 41 miles per gallon on the highway and 30 miles per gallon in the city. Surprisingly, this is a wagon, not a sedan, so that means there is a lot of space in the car. The car is very green and even takes the pollutants that the diesel creates and burns them off using the heat of the engine.
Volkswagen Golf TDI
Similar to the Jetta TDI is the Golf TDI. This hatchback gets 42 miles per gallon on the highway, and 30 miles per gallon in the city. Compare that to the gas version of the same model, and it gets about 30 percent greater fuel economy and much diesel fuel consumption when compared to gas.
The BMW 335d is the third best on the list, featuring 29 miles per gallon combined ratings. It has a big variance in highway and city numbers at 36 and 23 miles per gallon respectively. This car costs two times as much as the Jetta at $45,000. This is a global car, not just a European car, and the great highway mileage makes Americans want it that much more.
Mercedes also gets a mention here for its E320 sedan. It is very pricey, at over $52,000. It offers 32 miles per gallon on the highway, and 23 miles per gallon in the city. The sedan is built with Mercedes' "Bluetec" technology. This means the car runs on ultra low sulfur diesel, and any pollutants are run through a filter to make the emissions even less toxic. This car is only legal in 42 states, due to not meeting emissions standards by the strictest states such as California, and those in the northeast. It also gets 30 percent better mileage compared to the similar E350 gasoline powered sedan.
Jeep Grand Cherokee CRD
An American car makes the list, and that is the Jeep Grand Cherokee CRD. Jeep has made diesel cars since 2005, and they have been very popular. They may not have the high numbers, but remember this is an SUV. The Cherokee gets 25 miles per gallon on the highway, and 20 miles per gallon in the city, which is very respectable. Compare that to the gas Cherokee models, and that is a 25 to 30 percent improvement.
Does the Type of Fuel Used Affect Auto Fuel Efficiency?
Auto fuel efficiency depends on a number of factors. Diesel fuel is more fuel efficient than gasoline, due to the slower burning rate, however the cost per gallon of diesel fuel can be higher than gasoline, depending on volatile fuel prices, so it's greater efficiency may be a moot point depending on the economy and your driving practices. For a driver that makes a lot of long trips or does heavy work or hauling, the higher price of diesel will be offset by fewer trips to the pump.
It is a common misconception that higher octane fuels provide increased horsepower or better gas mileage. Unfortunately, this is not the case. Octane is really just a measure of how well the fuel resists engine knock, it does not boost fuel economy or horsepower.
Using completely different fuel types such as some of the alternative fuels available today can drastically affect auto fuel efficiency. Of course your car must be set up to be able to burn multiple fuel types.
Ethanol is an alternative fuel as well as an additive to gasoline and burns very fast. It produces a great deal of power, but is greatly lacking in fuel efficiency due to its fast burn rate.
Natural gas is close to the same fuel efficiency as gasoline, yet there are few fill up stations, and it is more expensive.
Hydrogen is a very efficient fuel that if it weren't for its danger and volatility would be a very viable replacement option for gasoline. Unfortunately, due to its hazards it cannot be used as a combustible fuel type yet. Hydrogen fuel cells are under development that can safely and extremely efficiently power a car, and the infrastructure necessary for hydrogen fueling stations is being studied.
Currently, there truly is no fuel that is both more efficient and cheaper than gasoline, but many technologies in development right now (such as electric cars, solar, etc.) have a very high likelihood of becoming and affordable alternative to gasoline in the future.