2010-model diesels are running well and turning in better fuel economy than their EPA-'07-spec predecessors, according to reports we've heard at industry meetings and in conversations with fleet managers.

Most truck operators who've bought engines whose exhausts are equipped with selective catalytic reduction aftertreatment systems say that fuel economy is at least as good as what manufacturers claim and in some cases is better.

What about the diesel exhaust fluid that's needed for this process? Spraying DEF into the exhaust to chemically neutralize oxides of nitrogen, or NOx, is the major action of the SCR used by almost all diesel builders. Like fuel, DEF is consumed in everyday running and should be accounted for in any economy reports or claims.

Navistar International, the one engine maker that does not use SCR, coined the term "fluid economy" to mean the total of DEF and fuel consumed in a given number of miles traveled. If DEF is figured in, Navistar executives claim, their fuel-only engines come out as good or better than competitors'.

So, how much DEF is being used? For over-the-road operations, manufacturers employing SCR predict DEF "dosing rates" of 2 to 3 percent. That means 2 to 3 gallons are consumed for every 100 gallons of diesel fuel, and 102-103 gallons of fluid should be factored into a mile-per-gallon calculation.

Truck operators are seeing those levels of DEF dosing, says Dave Michael, general manager of DEF for Mansfield Oil, which sells Air 1-brand diesel exhaust fluid from Yara North America. It has quizzed fleet managers about DEF consumption.

"Fleets tend to hold a lot of this information close to their chests," Michael comments. "With that said, the overwhelming response with regards to consumption ratio of DEF versus diesel is that the number is close to 3 percent. OEMs gave out a range of 2-3 percent when introducing SCR models, so it appears as though real-life scenarios are reporting back at the upper tier, yet still within the communicated range."

Michael also says that long-haul, over-the-road carriers are reporting 10 percent to 11 percent fuel economy improvements, running identical routes, comparing their new SCR units to '09 or older models.

"We have also heard some disappointment coming from regional, hub-and-spoke-type carriers that the fuel economy returns have been a bit lower than expected. We know it's highly dependent on service, road, route, etc., but we haven't seen anything less than promised from early OEM specs."

Chad Dombroski, Yara's director of Air1 operations, believes DEF consumption is generally 2 gallons of DEF for every 100 gallons of diesel. "We've seen some of the larger fleets recommend that their drivers refill DEF one out of every three times they stop for diesel."

He notes that the rate of DEF consumption will vary by fleet, truck, driver, and route. "On average, we've found that 2.5 gallons of Air1 DEF will yield over 350 miles of travel in the U.S., comparable to the distance between New York City and Youngstown, Ohio, and leads to significant fuel savings.

"For example, Volvo's reported fuel efficiency savings of 5 percent, and Penske's reported an 11 percent gain in fuel efficiency when comparing older engines to engines with SCR. Even if you account for the cost of DEF, which accounts for approximately 2 percent of fuel cost in the U.S. on average, depending upon price points and usage, most fleets and OEMs are still seeing a net savings gain of 2 to 9 percent in fuel economy, which can really add up when you multiply that across an entire fleet."

Chris Parker, shop coordinator for Sapp Brothers, a truckstop chain based in Omaha, thinks DEF use is higher. "They say it's a 2 percent dosing rate, but what we're having with customers is 3 and 4 percent," he says.

Sapp sells BlueDEF from Old World Industries, and by March had installed dispensers at truckstops in York and Odessa, Neb., and plans more as the need for the product increases. "The struggle is which side of an island to put it on," Parker says. "Peterbilt puts its DEF tanks on the right side of the truck, but the others put it on the left side. Drivers know where it is on their trucks" and line up accordingly, and it should be convenient for them.

Installing dispensers at fuel islands in cold climes takes some thought, because DEF turns slushy at 28 degrees and freezes at 11 degrees. Underground tanks are not the answer because of probable contamination of the fluid, which must remain pure to work in trucks' urea injection systems. Parker likes the idea of putting storage tanks in heated outbuildings, then plumbing underground below the frost line to the islands.

Some truckstops at first put bulk dispensers in buildings some distance away from fuel islands. That wasn't convenient for drivers, but locating dispensers at fuel islands is the trend. And as the population of new trucks with 2010-spec DEF engines increases, more will appear to better serve users, operators say.

Drivers are "pretty good" about keeping DEF tanks filled, Parker says. "They don't wait 'til it gets down to empty." A typical sale to a driver is 10 gallons, reflecting how little is needed compared to diesel fuel.

Early fears that DEF would not be available in the hinterlands are being dispelled, as fluid producers are striving to serve the increasing market for the stuff. Oslo, Norway-based Yara, for example, has erected a $1.8 billion urea production plant in Saskatchewan for use in Air1 DEF, and it has other facilities in the United States. Terra Environmental Industries has begun production of DEF at a facility in Oklahoma, where it will make 30 million gallons of TerraCair DEF per year.

The fluid's cost is coming down from when it first appeared on the market, when it was more than $12 per gallon. A NAPA auto parts store in Columbus, Ohio, sells a 1-gallon jug of Valvoline-brand DEF for $5.79 and a 2-gallon jug for $11.99. North of the city, a Flying J sells BlueDEF in a 2.5-gallon jug for $13.99, or $5.60 per gallon. The truckstop has installed an underground storage tank with fuel-island dispensers, and they should be operating by early June, a clerk says. The bulk price will be less than a third of the jug price, and at least $1.50 a gallon less than diesel.

If DEF cost about the same as diesel fuel, which is what some initially thought it would, the economics of urea injection would be a simple matter of subtracting the DEF dosing rate from the fuel economy improvement: If a truck gets 8 percent better fuel economy but uses 3 percent DEF, the net economy gain is 5 percent. Cheaper DEF means slightly more arithmetic, but truckers will have more dollars to take to the bank.

Form the June issue of Heavy Duty Trucking