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HOW WE IMPROVED OUR TRUCK'S AERODYNAMICS Roger Clark, GM's fuel economy guru, says these tweaks added at least 2 mpg to our gas mileage. 1. With no tonneau, plastic over the truck's bed smoothed airflow over the top. 2. By taping the grille, we improved airflow around the truck. 3. With no running boards, we blocked the gap between the body and frame rails.

Illustration by Jason Lee

HOW WE IMPROVED OUR TRUCK’S AERODYNAMICS Roger Clark, GM’s fuel economy guru, says these tweaks added at least 2 mpg to our gas mileage. 1. With no tonneau, plastic over the truck’s bed smoothed airflow over the top. 2. By taping the grille, we improved airflow around the truck. 3. With no running boards, we blocked the gap between the body and frame rails.

The Hypothesis When it comes to gas mileage, it’s not only what you drive but how you drive.

The Challenge Over 195 miles of interstate, get better gas mileage from a full-size truck than a midsize car. Use any means necessary to improve the truck’s mileage, but leave the car untweaked. (We added 600 pounds to each to simulate three passengers and their stuff.)

The Contenders Our truck of choice: a 5,879-pound Chevy Silverado LS 2500HD Crew Cab with a 6.6-liter turbodiesel V8 (diesels typically get better mileage). Trucks, sport-utes included, are subject to more aerodynamic drag because of their large front area and high ride height. To counter, we set the Chevy’s cruise control at 55 mph for the duration. Also, on the advice of GM’s Roger Clark, we altered the truck (see left) to improve mileage. The EPA doesn’t test heavy-duty trucks, but GM’s internal testing indicates 17 mpg on the highway.

Our car: a 3,313-pound Mercury Sable LS with a 3.0-liter dohc V6. With it we simulated “normal” driving-accelerating hard, passing at full throttle. A day before our experiment (on 55-mph cruise and sans the extra weight), our Sable logged 34.8 mpg through our course, better than its EPA highway rating of 28 mpg.

The Result Success! The Silverado clocked 26.0 mpg during our experiment, while the Sable got only 24.6 mpg. The price: We got home 40 minutes earlier in the Sable. And though it burned less fuel and created less carbon dioxide, the Silverado did belch more nitrogen oxides and soot. Nevertheless, it’s an impressive win for big trucks. Hypothesis proven.

-Dan Carney

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