Extreme Commuting: Diesel vs. Hybrid

Traffic
Diesels and hybrids have drastically different powertrains, but they both help commuters improve their fuel economy compared with a traditional gas-powered car. The 2013 Volkswagen Passat TDI with a six-speed manual and the 2012 Honda Insight hybrid achieve optimal mileage at highway speeds, but how do they stack up during miles of stop-and-go commuting?

The Passat's 31 mpg city rating is far off from the Insight's 41 mpg estimate. Game over, right? Not necessarily. During two nearly identical commutes, my observed results were much closer than the ratings suggest. 

Manual transmissions are the enemy of gridlock commuters. That is, unless you're in the Passat TDI. The silky smooth clutch pedal, easy shifter and engine torque that lets you chug along in any gear make driving the Passat in traffic a breeze. Returning 39.5 mpg on my commute is the reward, along with its quiet, comfortable and overall enjoyable ride. Bonus: This commuter car doubles as a people hauler, thanks to its massive backseat. This commute came at the end of a 1,500-mile road trip where, without hesitation, I was ready to get back in the comfy sedan and head to work.    

The 2012 Insight is a better commuter than previous versions, with more sound insulation that notably quiets the interior from wind and road noise. The Insight squeaked out a Passat-beating 44.5 mpg, but the start/stop feature that shuts the engine off to save gas at idle is intrusive and annoying. The noticeable shimmy every time the engine fires up or shuts down gets old quick. This routine happens frequently in bumper-to-bumper traffic.

The Insight may be more efficient and less expensive, but the fuel economy of the Passat TDI combined with its absurdly good observed mileage is impressive. 

Extreme commuting is defined by the U.S. Census Bureau as someone who spends more than 90 minutes per day on the way to the office. Since Cars.com is based in downtown Chicago, my commute lasts that long and can bring out the worst — or best— gas mileage in the cars we test. We track our fuel economy to give drivers with similar commutes an idea of what to expect in these conditions.
 
My real-world commute averages 37 miles one way from the western suburbs to downtown Chicago. It takes 90 minutes on good days and up to three hours on bad days. Those are really, really bad days. Speeds average 22 to 25 mph.

Like in our mileage challenges, data is collected from the car's on-board trip computer. As we've reported before, they are generally accurate, especially when calculating trips of this length.

PassatTDI_edited
2013 Volkswagen Passat TDI

  • Turbocharged 2.0-liter four-cylinder diesel, six-speed manual transmission
  • EPA rating (city/highway/combined): 31/43/35 mpg
  • Time: 1 hour, 47 minutes
  • Trip mpg: 39.5 mpg
  • Trip miles: 37.1 miles
  • Average speed: 21 mph
  • Outside temp.: 64 degrees

IMG_6647
2012 Honda Insight

  • 1.3-liter four-cylinder; 13-horsepower electric motor, CVT automatic
  • EPA rating (city/highway/combined): 41/44/42 mpg
  • Time: 1 hour, 45 minutes
  • Trip mpg: 44.5 mpg
  • Trip miles: 37.3 miles
  • Average speed: 22 mph
  • Outside temp.: 63 degrees

Related
More Extreme Commuting Results
2012 Honda Insight Review
2012 Volkswagen Passat Review

Comments 

B Sharpe

Interesting, real-world observations. I have heard 50+ mpg bantered about for the TDI, but this may be for 60 mph on open highways, so the congested rating is still good. Of couse other considerations arise when comparing hybrids to diesels. Initial purchase premiums, environmental concerns, resale prices as batteries age, etc. I'm an old Rabbit diesel fan and they're great commuters, but past functional obsolecense for some folks.

nick

From personal experience, a TDI gets 38-40 MPG in real world driving. A small gas car gets about 10 less (28-30). If you factor that diesel fuel and car cost more, it is a toss.

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