What do the rating stars mean?
From the built-in toolboxes in the cargo bed to the “protect from the scuffs of work-a-day life” seat covers, our tester was upscale and comfortable, yet outfitted for hard work and flexible-fuel efficiency. Jammed with LT2 Convenience Package goodies, it definitely kept its workin’ attitude with the GM Performance package and 315 HP engine with 338 ft-lbs of torque. This Silverado earns an EPA rating of 14/19 for its 5.3-liter Active Fuel Management V-8 and has a base price of $34,710. Our tester was optioned out at $43,025 and included a 5-year/100,000-mile powertrain warranty.
Initial Impression: Got the glam—does it got the go?
Scott: "The look of the Deep Ruby Metallic paint and a glance at the chrome-tipped Cat-Back exhaust made me like this truck right away. I had always enjoyed driving the GM flex-fuel V-8s for both their power and their economy, and I knew that Active Fuel Management was part of GM’s engine efficiency strategy. And yes, I had an idea or two how I’d like to test out its economy limits."
Christine: "I’m a car gal at heart and it takes a lot to get me excited about a truck … would this big guy be good for this girl or better suited for a workin’ man? Time to climb behind the wheel to see if this one would win me over."
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Look & feel: More than a toolbox on wheels
For the second year of the new design and the refreshed exterior, the Silverado still looks really good—we think it’s one of the nicest exterior treatments GM has created in quite a few years. Though our tester didn't have the premium interior package, it did have the Light Titanium leather upholstery and was outfitted with dealer installed heavy-duty seat covers. Trucks can be harsh when unladen, but not here. The ride was smooth and forgiving, even on choppy back roads; it had a safe and secure feeling with plenty of power on tap when needed. And the throaty rumble of the low back pressure free-flowing Cat-Back exhaust system was part of the performance package that gave this truck a satisfying growl.
Best of all, it was easy to goose extra mileage out of the engine. Even with its deep rear gear, the truck would coast easily after lifting off the throttle (the secret of efficient driving), without needing to constantly stab the brakes or lay on the accelerator. Scott loved the way he could drive “light on the throttle,” and flow with traffic. We both liked the silky smooth transmission—never felt a shift.
Unfortunately, the dealer-installed toolboxes precluded us from hauling any substantial cargo, so we can’t comment on how it would handle with any real weight in it. We always like to throw a big garden tractor or go-cart in the back of our testers to see how they haul—though with the Z85 suspension, we doubt it would be an issue.
Fuel-ability: How much flex is in that fuel?
Just to see how we could affect fuel mileage, we experimented with E85/gasoline mixes. Ordinarily, when we test drive an FFV, we start out with a tank full of gasoline, drive through various road conditions and note the average fuel economy. Next we’ll fill ‘er up with E85, and drive pretty much the same set of circumstances and note the differences. This time we added E85 to the tank in varying ratios to slowly dilute the mixture, with each fill-up bringing the fuel load closer and closer to 100 percent E85. Our point? See if we could hit a sweet spot where the fuel blend (say 50/50) would yield the best economy per total cost per mile driven.
At the time we tested our Silverado, regular gasoline was selling for $3.05 a gallon and E85 was priced at $2.07. Wow indeed, just about a buck cheaper for E85 … not only cleaner emissions, it’s often cheaper per mile even with the inherent fuel economy drop off. And this is the problem with flex-fuel engines—because they must be able to burn both gasoline and E85, they can’t take advantage of E85’s superior 105 octane rating. It’s the main reason fuel mileage is lost with E85. Because it has lower energy content (82,000 BTU/gal) than gasoline (114,000 BTU/gal), more fuel is required to deliver the same power. Depending upon a host of engine characteristics, from cylinder compression ratio to valvetrain geometry and drivetrain variations including overdrive and final gear ratio, each FFV experiences its own unique response to fuel economy loss on a diet of E85. So how’d our V8 Silverado do when we crunched the numbers?
The Enviro-meter: Mean, but still clean
Well, we were surprised at the results. Pleasantly. We logged a respectable 16.3 mpg on gasoline and our first top-off with E85 (about 11 gallons yielding 40 percent dilution), knocked our mileage down to 15.3 (about 6 percent). A second addition of 6 gallons of E85 (now about 60 percent dilution) dropped our economy down to about 14.5 (10 percent drop from all gasoline). We never got to a 100 percent E85 test, and since our experiment was hardly scientific, we can’t say with absolute certainty what the mileage would have been. But based on this experiment and a little extrapolation, we figure the final tally would have been somewhere around 13.3 mpg (about 18 percent less than gasoline.) Many of the flex-fuel V-8s we’ve driven had some pretty harsh economy loss with E85 (25 percent or more), so our Silverado’s results were a nice treat. And with this engine, there really is no sweet spot; the mileage decline is slow and steady but never severe.
So what is going on here? The fuel injectors play a role in enabling a flex-fuel engine to burn varying concentrations of E85 and gasoline. Higher concentrations of E85 require increased injector pulse width, obviously increasing fuel consumption. It’s not all bad news: GM’s Active Fuel Management (cylinder deactivation) helps soften some of the economy losses by shutting down cylinders when not needed (V-4 mode).
On a diet of E85, this flex-fuel engine consumes 6.7 barrels of petroleum; its gasoline counterpart would consume 21.4 barrels. The carbon footprint: 9.2 tons of C02 for E85 and 11.4 for gasoline.
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