Clean Diesel: More Efficient Than the Prius?

By Todd Kaho 

How do modern clean diesel cars stack up in the real world compared with fuel-efficient gas cars and super-efficient hybrid models, such as the Toyota Prius? Depending on the type of driving you do most, you may find diesels have an edge.

To see how clean diesel measured up, I tested the 2012 Volkswagen Jetta TDI against the Prius and the Ford Focus. I’ve noticed some diesels and hybrids didn’t receive the best mileage figures in the 2008 and later EPA tests. Know that your mileage will vary based on your driving habits, but with both the Jetta TDI and the Prius, exceeding the official miles-per-gallon numbers is definitely possible.

In my test of the Jetta, I was able to average in the mid-40s for city mpg and more than 50 mpg on the highway without much effort. The Prius had the upper hand in city driving, with about 51 to 52 mpg, but only 47 mpg on the highway. Then there’s the traditionally efficient Ford Focus, which achieved a respectable 28 mpg in the city and 38 mpg on the highway.





2012 Volkswagen Jetta TDI


2012 Toyota Prius III


2012 Ford Focus SE


2.0-liter, 4-cylind. turbodiesel

1.8-liter, 4-cylind. gasoline-electric

2.0-liter, 4-cylinder gas


6-speed auto.

auto. CVT

6-speed auto.

Base Price 




EPA City/Highway MPG 




Real-World MPG Estimate      




Range at Highway MPG 

559 miles

521 miles

421 miles

Fuel Capacity 

14.5 gallons

11.9 gallons

12.4 gallons

Annual Fuel Cost 




Powertrain Longevity 




Interior Room 

94.1 cubic feet

93.7 cubic feet

90.7 cubic feet





Air Pollution Score 




Greenhouse Gas Score 




Drive Score 




Base Price: Manufacturer’s suggested retail price + destination fee

Annual Fuel Cost: Based on 45 percent highway, 55 percent city driving, 15,000 annual miles, with diesel fuel price = $4.05 per gallon, gasoline = $3.75 per gallon

Powertrain Longevity: 1 = worst, 5 = best

Air Pollution Score: Zero = most tailpipe emissions, 10 = least

Greenhouse Gas Score: Zero = most greenhouse gas emissions, 10 = least

Drive Score: 1 = worst, 5 = best (based on overall operating experience: fun to drive, acceleration, cornering and braking)

Read more: Find more details about clean diesel vehicles and diesel engines, including how they work and which automakers offer them, in Clean Diesel: A New Era of Green Cars, and see a 2010 comparison of the Volkswagen Jetta TDI, Toyota Prius III and Ford Focus SEL in Clean Diesel: Greener Than the Prius?.

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