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On Road to MBS, Hybrid Beats Diesel in Fuel Race

Ward’s editors driving to northern Michigan for the annual automotive Management Briefing Seminars selected the ’10 Toyota Prius and ’09 VW Jetta TDI SportWagen for fuel-economy comparisons.

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Management Briefing Seminars

TRAVERSE CITY, MI – With a journey of about 200 miles (321 km) to the Center for Automotive Research’s Management Briefing Seminars here, Ward’s sets out to prove which powertrain can deliver the best fuel economy – a diesel or a gas/electric hybrid.

The timing couldn’t be better. Gasoline prices peaking last summer at $4 a gallon have pushed fuel economy to the forefront for many consumers. Plus, there are many new diesel and hybrid vehicles on the market this year boasting the latest powertrain technology.

Ward’s selected two obvious candidates: the all-new, third-generation ’10 Toyota Prius hybrid-electric vehicle and ’09 Volkswagen Jetta TDI, sporting a thoroughly modern common-rail 2.0L turbodiesel. Both are well-equipped; the Prius stickers at $32,720 and the Jetta SportWagen TDI at $28,310.

First, the rules: To make it a fair fight, we zeroed out our mileage counters, checked the air pressure in our tires and began our trip at the same point – a gas station near where we accessed the interstate highway.

We made sure each vehicle was carrying about the same amount of cargo and kept windows closed on the highway, with the air conditioning set on low. Driving 2-lane highways off the interstate, we shut off the AC and cracked the windows a few inches.

We agreed to keep interstate speeds close to 70 mph (112 km/h). Both exited at the same northern Michigan town and followed the identical detour around a construction project. We ended our journey a stone’s throw from the Grand Traverse Resort here, where the week-long automotive management conference is being held.

Here are the comparison details:

Tom: The new clean diesels rule, and I was fully prepared for the Jetta TDI to slay any comer in a fuel-economy battle.

Christie: Sorry, pal. The hybrid beats your diesel any day of the week. The Prius performed like a champ. Not only was it exemplary in lower-speed driving, but I smoked you on the highway portion too.

Tom: Yes, my numbers didn’t stack up. On the first leg of our trip the Jetta averaged 39.5 mpg (5.9 L/100 km), and on the second leg, off the interstate, it managed 44.0 mpg (5.3 L/100 km).

Christie: The Prius averaged 48.3 mpg (4.8 L/100 km) on the interstate. But once on the 2-lane roads, it returned an astonishing 60.1 mpg (3.9 L/100 km), easily making the HEV the victor.

Tom: OK, but I recall a Volkswagen turbodiesel long-term Ward’s loaner in 1997 that routinely delivered 45 mpg (5.2 L/100 km) on the highway. I was certain the new TDI would be even better. It’s certainly more enjoyable to drive (and didn’t belch smoke, either). But the numbers fell short of the Prius.

Christie: Even though the Prius earned overall great mileage, the numerous hills in northern Michigan quickly sapped its fuel economy. Drivers following me on a twisty 2-lane portion of the road were seething as the hybrid slowly crept to the crest of each hill as I sought to avoid the dreaded “Power Mode,” a source of great shame for hyper-milers.

Tom: I drove the same roads but didn’t notice any hills. The tremendous torque surge (236 lb.-ft. [320 Nm]) of the mighty TDI flattens just about any surface. This part of the contest was no contest at all. Early on in the trip, a gravel hauler started swerving and spilling some of its cargo on the interstate. Rather than wait for debris to strike the windshield, I put the pedal down ever so slightly and the Jetta zipped on by, out of harm’s way. Let’s see the Prius do that.

Christie: I was really missing the TDI’s torque, especially driving in the hybrid’s wimpy “Eco Mode,” which can be held only with a steady throttle. The Prius, using lights on the dashboard and a certain sensation in the pedal, lets the driver know when she’s asking for too much power. A Sunday drive can become a guilt trip.

Tom: I respect the Prius but can’t say I enjoy driving it the way I do the TDI. I only can bond with a vehicle that has a great engine, one that doesn’t flinch at tall downshifts or wide-open throttle. The new clean diesels do it for me.

Christie: Even though Toyota has engineered tighter steering, more confident handling and slightly more growl for the new Prius, I agree there’s still a cold, mechanical interface that keeps the driver at a distance – making for a pretty dull driving experience. The only fun I had during our race was watching the Hybrid System Indicator and knowing the Prius was going to win.

Tom: Did I mention the Jetta is black, which soaks up the sun’s heat, requiring more cabin air conditioning and lowering fuel economy, according to the California Air Resources Board…

Christie: Give it up already.

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