Mileage Challenge 7.2: The Results

Gas, diesel or hybrid? That’s the question we set out to answer in our latest mileage challenge of small, sporty cars.

There’s the hybrid Honda CR-Z, the diesel Volkswagen Golf TDI and the conventionally powered Mini Cooper. Combined EPA fuel-economy ratings for all three cars fall within 2 mpg of each other, but each car takes unique fuel. The Cooper sips premium gas, and the CR-Z takes the cheap stuff; the Golf TDI needs diesel.

Each car’s trip computer offered a gas-mileage readout, which we reset to begin each of the three legs on our 330-mile daylong route. The winner came down to the car that had the lowest fuel costs over a 15,000-mile year of driving, given our observed mileage.

The scrutiny, it turned out, made little difference. Each hatchback handily beat its combined city/highway EPA fuel-economy rating, but the Golf TDI ran away with the gas mileage and remained victorious even after we accounted for the high cost of diesel.

Check out the results below.

We would have entered the fuel totals into the chart above, but the results were bewildering enough to warrant discounting them. At day’s end, the Cooper took 9.68 gallons of premium fuel; the Golf TDI took 7.87 gallons of diesel. Those worked out respectively to 34.1 and 42.4 mpg. That’s spot-on with what the TDI’s computer said, and within a reasonable margin for the Cooper.

The CR-Z, however, took just 6.97 gallons of gas. That works out to 46.9 mpg, or 24 percent higher than the trip computer’s mileage readout. We cried foul: Those numbers fall way too far outside a conceivable range. We filled each car with fuel to begin and end the day to a visible level below the filler neck (we did this strictly for accuracy; don’t do this at home), but we’ve seen wonky pump readouts before. Fill-up calculations tend to be reliable over time, but as we’ve reported, shorter mileage evaluations put more emphasis on trip-computer readouts. (Still, at least one government study has questioned the reliability of the readouts.)

Thus, we went with the trip computers, and the TDI won the day. This is Volkswagen’s second strong showing; in another daylong drive, a 2009 Jetta TDI came less than 1 mpg short of a Toyota Prius, despite the Prius’ 17-mpg higher overall EPA rating. Had we found a CR-Z with its optional continuously variable automatic transmission, things might be different. It’s EPA-rated 3 mpg higher than the six-speed manual, but the stick-shift is what Honda had on hand. (A Golf TDI with the standard six-speed manual, on the other hand, may not have changed the results; like the TDI automatic, it has a combined 34 mpg EPA rating.)

The cost of diesel fuel kept Volkswagen from knocking this competition out of the park. Diesel prices currently run about even with premium unleaded; it’s a big shift from a year ago when diesel was about the price of midgrade. (Calculated then, the TDI would have been ahead of the runner-up CR-Z by $63, not $29.) Still, all three did fairly well: A four-cylinder Honda Accord, by comparison, would cost $1,572 in projected annual fuel costs.

The price difference to fuel these three cars came to less than $200 a year. Over the course of five years that would mean you’re paying a premium of $1,000 just in fuel costs to own a Mini Cooper over a VW Golf TDI. There’s one other thing to consider: how they drive. With costs this close, the driving and livability of the three is of utmost importance. We’ll delve into that tomorrow, but for now check out the faceoff of the three cars. 

Details on the routes are below. It’s worth noting that if heavy urban traffic were all you drove in, the CR-Z would be your best bet. The first 35 miles of Leg 1 took us the length of Chicago’s surface streets, which is the sort of grueling urban route reminiscent of our second mileage challenge. Averaging just 18 mph, the Cooper registered 28.3 mpg, while the Golf TDI got 30.5 mpg. The CR-Z topped the group with 32.7 mpg.

More on the routes:

Leg 1: 84° F, sunny
Traffic: Medium (5/10)
Average distance: 109 miles
Average speed: 30 mph

Leg 2: 88° F, sunny
Traffic: Light (2/10)
Average distance: 110 miles
Average speed: 58 mph

Leg 3: 91° F, sunny
Traffic: Heavy (7/10)
Average distance: 111 miles
Average speed: 33 mph
Source: The Weather Channel
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