As the industry gains long-term experience with diesel exhaust fluid (DEF) – a liquid critical to the proper operation of selective catalytic reduction (SCR) emission control technology on trucks – concerns about the cost and performance seem to be subsiding.

“At every event we attend, we see fewer people who do not know of DEF, a few that are afraid of it, but almost no one that has had a bad experience,” Frank Cook, senior Vp-new product development with Peak Commercial & Industrial, told Fleet Owner.

“In the simplest of terms it [DEF] allows the engine to run in an optimal performance range and eliminate some EGR [exhaust gas recirculation], he explained. “Those actions improve fuel economy and [while] it produces more NOX [oxides of nitrogen] that is now treated in the SCR system.”

In an online survey Peak conducted last month, Cook said one of the top concerns voiced by trucking industry respondents about DEF and SCR centered on fuel economy.

Yet he noted that with the typical “treat rate” of 3% DEF per 100 gallons of diesel used saved roughly $12 with diesel at $4 per gallon. And since DEF costs less than diesel, that results in lower operating costs for truckers.

“For every dollar spent on DEF, it is about 40 to 50 cents less you are spending on diesel fuel, which is a solid return rate,” Cook noted, adding that the typical trucker need only fill their DEF tank once every 6,000 miles.

And that price differential may be improving. According to data tracked by international research firm Integer, the U.S. national average price for DEF tote refills dropped six cents to $1.91 per gallon last month compared to July, while in Canada, DEF prices also declined by two cents CAN $0.57 per liter (roughly US $2.25 per gallon) in August as well.

DEF truck stop prices are also remaining remained stable at $2.79 per gallon in the U.S. – the same price point held since November 2012 – and at CAN $0.80 per liter in Canada (equating to some US $3.01 per gallon) since October 2011, the firm said.

Integer added that Salt Lake City, UT, posted the highest average price for DEF tote refills while Cincinnati, OH, and Atlanta, GA, registered the lowest average prices amongst all areas covered in the U.S.

Peak’s Cook also noted that other performance concerns about DEF seem to be lessening as well.

“I think people were afraid that any freezing [of DEF] would lead to other problems, but the truck systems thaw the DEF when the engine is started,” he explained. “In bulk quantities it takes a lot of sustained coldness to pull that amount of heat from a system to freeze it. Freezing just hasn't been a problem.”

Cook added, though, that longer term benefits to truck systems from SCR/DEF usage still remain unclear as of yet.

“Time will tell,” he stressed. “The benefit of SCR is eliminating EGR which generated a lot of heat, robbed fuel economy, cooked antifreeze and oil and seemed to hurt overall engine life. Everyone involved in engines and truck building is attempting to answer this question and improve performance and life. Experience with the new SCR vehicles will tell the tale.”