Real World Challenges with Diesel Exhaust Fluid


Though we’re more than halfway through 2010, it can be a challenge to find and use diesel exhaust fluid, as we found out recently during our 2010 Heavy-Duty Shootout comparison test in Michigan.

We staged all of our long-distance testing out of the Pilot Travel Center in Dexter, just west of Detroit. It’s currently the only Pilot location in the state where DEF is dispensed at a self-service pump outside next to diesel fuel pumps, instead of sold in bottles.

Pilot has been a leader across the country, but the DEF pump in Dexter was out of order while we were there, and Pilot staff said it had only worked sporadically since it was installed several months ago.

What’s the big deal about DEF?

On Jan. 1, tough new EPA emissions regulations required all new diesel engines to reduce nitrogen dioxide emission levels by 90 percent from 2007 and by 96 percent from 1994.

NOx is a major air pollutant that contributes to smog, asthma and respiratory and heart diseases. It's a byproduct of diesel’s high combustion temperatures, which result from the high frictional heat levels created by compressing air in the cylinders to the point where it can ignite diesel fuel without a spark. DEF in diesel-powered pickup trucks uses urea selective catalytic reduction to lower the emissions.

Truck manufacturers have split into several camps over which NOx reduction method is best for their trucks. Pickup trucks that require DEF include the 2011 Ford F-Series Super Duty, powered by the all-new 6.7-liter Power Stroke V-8, and the 2011 Chevrolet Silverado and GMC Sierra HD pickups, powered by the updated 6.6-liter LML Duramax V-8.The Ram truck lineup uses two different methods to scrub NOx. Ram 2500 and 3500 pickup trucks use a urea-free NOx absorber catalyst that doesn’t require DEF, while Ram 3500, 4500 and 5500 chassis trucks use urea SCR and DEF.

Because diesel trucks that run out of DEF are no longer emissions-compliant, they are virtually immobilized when the DEF tank runs dry, even if there’s diesel fuel available to keep them trucking. Ford, GM and Chrysler have similar strategies to alert drivers when their DEF tanks have 1,000 miles or less range left, so modern diesel drivers won’t get stranded on the side of the road.

We were fortunate because all of our trucks’ DEF tanks were still more than half full. It would have been inconvenient if they needed to be refilled.

Pilot’s pump price for DEF was a reasonable $2.99 a gallon, compared with almost $32 a gallon that Consumer Reports recently paid a Mercedes-Benz dealer to refill a GL SUV. Inside the Pilot store in Dexter, a one-gallon bottle of DEF cost $5.99, though Pilot staff graciously reduced that price to $2.99 because the DEF dispenser wasn’t working.

Photo courtesy of Diesel Power Magazine / David Kennedy

Check back August 16 for the full results of our 2010 Heavy-Duty Shootout, including the results of our first-ever DEF usage test recorded during our 300-mile fuel economy loop.


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