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2014 GMC Sierra Denali 1500 4WD Crew Cab Update 4

Motor Trend logo Motor Trend 11/17/2014 Frank Markus, Motor Trend Staff

Our handsome hauler hit the sauce pretty hard late this summer, swilling some 215 gallons of pure corn ethanol, cocktailed as it was with 38 gallons of gas dispensed from yellow E85 pumps. This being my first long-term test vehicle with a yellow gas cap, I was eager to prove the paradigm that despite the attractive pump pricing, E85 isn't enough cheaper than gas to compensate for its lower energy content.

Except it was cheaper the way this truck burned it. I'm comparing 3,726 miles of E85 consumption (split 48/52 percent city/hwy) with the 3,512 miles of gasoline operation immediately preceding it (split 41/59 percent). The weather was similarly temperate throughout the test, the tonneau was fitted the entire time, and the engine was fully broken in at 11,399 miles at the start of the test.

E85 reduces realistic driving range to 300-350 miles, so locate fuel stops before you leave if planning to fuel a long trip on E85© Provided by MotorTrend E85 reduces realistic driving range to 300-350 miles, so locate fuel stops before you leave if planning to fuel a long trip on E85 We averaged 14.7 mpg on E85 versus 16.8 mpg on gasoline, revealing less of a drop in mpg than the EPA predicts — city/hwy/comb ratings are 12/16/13 on E85 and 16/22/18 on gas. I doubt driver behavior skewed toward babying the throttle during the E85 test, as many of us knew about and were eager to experience E85's added performance.

In any case, our actual fuel cost on E85 dropped to 20.1 cents/mile from 22.1 cents on gas. Concerned that advantageous Midwestern E85 pricing or generally falling fuel pricing might have skewed our results, I substituted the June-September national average price for each fuel ($2.83 for E85 and $3.63 for gas*) and came up with 19.3 cents/mile on E85 versus 21.6 for gasoline.

As for the performance boost, our 5.3-liter V-8 is rated to produce 7 percent more horsepower and almost 9 percent more torque when running on E85 (380 hp/416 lb-ft versus 355/383), so at the end of the test when the truck was well-calibrated to E85, I ran numbers and found it accelerates to 60 mph 0.3 second faster (7.1 versus 7.4) and hits the quarter mile in 15.5 seconds at 90.5 mph versus 15.8 at 88.0. Running E85 won't be mistaken for dropping in a 6.2L or some turbos, but every little bit helps.

2014 GMC Sierra Denali 1500 Crew Cab© Provided by MotorTrend 2014 GMC Sierra Denali 1500 Crew Cab Apart from the slightly sweeter smell when refueling, the only other noticeable difference was longer cranking during cold starts. On a few chilly mornings at the end of the test, the automatic-start feature cranked two or three times as long before starting as it does with gasoline -- an effect that will likely worsen as temperatures fall. The other hitch is finding E85. The nav system's database of E85 stations is incomplete and sometimes incorrect, leading one driver to actually run out of E85. For that reason, we've intervened and put Jim back on the wagon.

2014 GMC Sierra Denali 1500 4WD Crew Cab Update 4

*Sources:E85prices.com and eia.gov

An editorial epilogue about the earth-friendliness of E85: The slight cost savings incurred by driving our truck on E85 is the only reason I see for doing it, and it's an admittedly selfish one. I can't reasonably claim to be reducing my carbon footprint by any more than the 0.22 lb/mi difference we measured in our testing (0.93 versus 1.15 lb/mi). "But growing the corn sucked up CO2!" you protest. Yes, but that corn was destined to be planted anyway, and it sucked up that same amount of CO2 whether it was fed to an animal or burned in a chrome-bedecked GMC, so no more CO2 left the atmosphere as a result of this transaction, and a whole lot of water was used to grow it that might have been better used for something else. Little or no E85 in the pipeline today comes from waste sources such as corn stover that would have otherwise rotted and released the CO2 it absorbed while growing, or from corn fields planted in previously non-arable land that wasn't already taking up CO2. And with oil prices seemingly on a steady decline, don't hold your breath for economically viable cellulosic ethanol any time soon.

More on our long-term GMC Sierra Denali 1500 4WD Crew Cab:

2014 GMC Sierra Denali 1500 Crew Cab© Provided by MotorTrend 2014 GMC Sierra Denali 1500 Crew Cab
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