The Prince of Parsimony: Squeezing 70 MPG from a Chevy Cruze Diesel

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This is a simple hypermiling test. Take a 2017 Chevrolet Cruze Diesel, turn off the A/C, keep the windows rolled up, get on a California freeway, set the cruise control at 55 mph (10 mph under the limit), and see what sort of fuel economy results. Touch the brakes and throttle as little as possible, and return with a mileage number.

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In May, we published an instrumented test of a nearly identical Cruze Diesel automatic and reported on how it performed on C/D‘s usual highway fuel-economy loop—200 miles at 75 mph over the Michigan flatlands. As Joseph Capparella reported, that Cruze returned a thick 52 mpg, delivering a beat down to the Toyota Prius by a 6-mpg margin on a loop designed to be a “real world” test, not optimized for ultimate parsimoniousness. This time, we (by which I mean me) would actually try to get good mileage.

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So I acquired a Cruze Diesel sedan practically identical to what Capparella had reviewed. Both had the 137-hp, aluminum turbo-diesel 1.6-liter inline-four, both wore 16-inch wheels wrapped in Goodyear tires, and both had the optional nine-speed automatic transmission.

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On the ninth day of June, a Friday, the slate-gray Cruze was filled at pump 5 at the Winchester 76 in Goleta, California. The tank was topped off until the automatic stop on the pump handle snapped itself off twice (in between, it was left to rest for 10 seconds while fuel settled in the tank). Winchester 76 was chosen because it pumps diesel, it’s at the far northern edge of the Santa Barbara metropolitan area beyond the reach of likely traffic jams, there was a nice downhill entry onto the northbound lanes of the US 101 freeway, and it’s close to where I live.

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I started driving at 1:30 p.m., there was no wind, and the temperature was 72 degrees. Barely touching the throttle, I let the car get to 55 mph as slowly as it could. Once at 55, I engaged the Cruze’s cruise control, started playing the Tony Kornheiser Show podcast on my iPhone, and didn’t get off the freeway until the Traffic Way exit in Arroyo Grande about 77 miles later. After driving through Arroyo Grande, I feather-footed it back onto the freeway southbound. And at 55 mph I re-engaged the Cruze’s cruise. C’est La Cheeserie.

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Except for a stop in Santa Maria at Central Coast Hot Rods and a late lunch in adjacent Orcutt, I stuck to my freeway troll. Back at the Winchester 76, I pulled the Cruze back up to pump 5 and again refilled the tank with diesel following the aforementioned procedure endorsed by C/D‘s tech wizards.

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The driving experience? Utter, boring misery. Headed northbound, I was passed by clapped-out old Hondas, a Ferrari FF and a McLaren 570GT flying in formation, and trucks hauling stacked junkers. And on the way south, a ’64 Ford Fairlane blew by me. I only once had to slow, for a timidly driven Nissan Altima. The ventilation system in the Cruze works great with air conditioning, but with A/C off the interior got sticky and stinky with Pearley sweat.

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While this long section of the 101 freeway is lightly trafficked, it has geographic challenges. There’s a long grade skyward south of Nojoqui Falls, and the road snakes up and down along the foothills that frame the Santa Ynez Valley. You want boring photos? I’ve got boring photos of fuel going into a gray Cruze.

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The bottom line: I started this trip with 3346 miles showing on the odometer, and it ended with 3505. The trip odometer showed 159.0 miles. It took 2.257 gallons according to pump 5 to fill the car back up. The math is simple, but the result is astonishing. This works out to a gob-smacking 70 mpg. I was expecting 60 or maybe 65 mpg.

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I stipulate to plenty of caveats here. The drive relied on the Cruze self-reporting its odometer, there are likely much better ways to measure how much fuel was consumed, and no one from C/D’s crack tech staff was on hand to add some subtlety and elegance to the exercise. This is back-of-the-envelope science performed by a guy with a Poli Sci degree from UC Santa Barbara. And despite all that . . . 70 mpg is an epic number. The official fuel capacity is 13.7 gallons, so go ahead and try to match it. You should be able to experience extreme boredom for more than 900 miles before needing to refuel.

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The supertrick elements at play here are the turbo-diesel’s outstanding flat torque curve that peaks at 240 lb-ft at only 2000 rpm and the wide spread of gears in the Ford and GM co-developed 9T50 nine-speed automatic. Despite running a tall 3.17:1 final-drive ratio, the engine was able to stay in the deep overdrive of ninth gear practically the whole trip. That kept engine speed at a resolute 1500 rpm almost the entire trip. The one time the transmission shifted down was climbing the long Nojoqui Grade, and even then it only rose to the 2000-rpm torque peak.

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Instrumented Test: 2017 Chevrolet Cruze Diesel Automatic

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Cadillac Diesel Program Continues, Despite Opel Sale

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Chevrolet Cruze Research: Reviews, Specs, Photos, and More

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There’s plenty to criticize about the Cruze Diesel, as pointed out in that earlier full road test. The ride is unforgiving, the handling is uninspiring, and it’s not roomy. But the fuel mileage—EPA-rated at 31 mpg in the city and 47 mpg on the highway—is stunning. Hybrids—including Chevy’s own Volt—will beat its efficiency in stop-and-go traffic, where regenerative braking and batteries give them a definite edge. But for constant-speed highway commutes? Diesel kicks ass. In light of Volkswagen’s diesel-emissions debacle, it’s questionable whether diesel passenger cars have a future in America.

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But . . . 70 mpg.

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