2009 Volkswagen Jetta TDI
Hybrid vs diesel: It's a longstanding green-car conundrum. Which is better, a hybrid-electric vehicle that recaptures wasted energy in a battery and uses it to assist the gasoline engine, or an efficient modern clean diesel that goes further on a gallon of fuel?
The answer depends in part on your duty cycle, or how you use the car. Hybrids are most efficient in stop-and-go urban traffic (think New York City taxi), whereas diesels get their best mileage on long, high-speed freeway travels (think NY-to-LA road trip).
Real-world report: 39.2 mpg highway
Now our sister site, VolkswagenReports.com, reports that author Tim Healey was able to achieve 39.2 miles per gallon over a 540-mile road trip mostly made up of high-speed cruising--and 36.3 mpg overall--in a 2009 Volkswagen Jetta TDI sedan.
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2009 Volkswagen Jetta TDI
2009 Volkswagen Jetta TDI Sportwagen
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2009 Volkswagen Jetta TDI Cup racer
That 39.2-mpg figure almost precisely matches the 39.5 mpg achieved by Ward's Auto writers on another long road trip, in which they matched their own 2009 Jetta TDI against a brand-new 2010 Toyota Prius hybrid hatchback.
Note that the EPA rates the Jetta TDI at 29 mpg city / 40 mpg highway. Diesel fans have long complained that today's clean diesels, including the Jetta, get much higher-than-EPA mileage figures in real-world use.
EPA's 40 mpg: On target
But this makes two reports showing that, at least for highway travel, the EPA's mileage figure for the Jetta TDI is pretty much on the money.
That said, in the Ward's test, the 2010 Prius (EPA rated at 51 mpg city / 48 mpg highway) still trounced the 2009 Jetta TDI, returning 48.3 miles per gallon on the Interstate (vs the TDI's 39.5 mpg) and a jaw-dropping 60.1 mpg on slightly slower rural roads (against the Jetta's 44.0 mpg).
Any vehicle that returns 35 mpg or more in real use is more fuel-efficient than the vast majority of new cars today.
And after a point, the differences are more about bragging rights than about saving usefully significant amounts of fuel. Because MPG is not a linear scale, the actual gasoline saved over 100 miles by going from 40 to 60 mpg is less than 1 gallon.
Author Healey liked the Jetta TDI's "torquey diesel, the exemplary fuel-economy numbers, and the large rear trunk," while his friend and travel companion John lauded the reclining passenger seat.
They were less thrilled about the hard seats, excessive tire noise at speed, and out-of-date electronics. Healey called the navigation system "slow on the job sometimes", wished for an (unavailable) Bluetooth connection, and pointed out that the "available MP3 player did not work with my iPod Touch or John's iPhone, forcing us to use the less convenient auxiliary hook-up."
Still, despite some body roll, he echoed other reviewers' take that the Jetta TDI is a good driver's car, with the diesel's ample torque making it feel sportier than perhaps it is. The same can hardly be said about the 2010 Toyota Prius hybrid.
Finally, it's worth noting that the current Jetta sedan, which launched as a 2005 model, will be redesigned for 2011--just as the 2010 Golf hatchback already has been. We think the 2010 Volkswagen Golf TDI may be clean diesel's biggest winner in the US market.