Mario Enriquez says there’s no real trick to getting great fuel mileage in a big truck. "Just take it easy," says the 61-year-old native of El Paso, who’s driven an 18-wheeler for 11 years. "I don't gun the engine, I just gradually give it the gas." Enriquez averaged 9.74 miles per gallon from February to April in an International ProStar made by Navistar International Corp. For that, his employer, Mesilla Valley Transportation (MVT), awarded him a Nissan Versa compact car. Enriquez wasn’t even the best of the company’s drivers in the latest quarter, but no driver is allowed to win more than once and all those ahead of him were previous winners. The mileage performance Enriquez and truckers like him can achieve with current trucks is significant because it could influence how far the U.S. government pushes heavy truck makers to boost the average fuel economy of future Class 8 trucks – the over-the-road haulers like the ones MVT operates. Environmentalists want the Environmental Protection Agency to set a standard of 10 miles per gallon, up about 40 percent from current levels, as part of a broader effort to curb U.S. greenhouse gas emissions. Some truck manufacturers say that could be too aggressive. But owners of truck fleets such as MVT are running ahead of regulators and manufacturers, taking advantage of new technology and new ways of motivating drivers to cut fuel consumption. Their primary goal is cutting fuel bills, one of a trucking company’s biggest costs. In the process, some truckers are already achieving mileage close to the target that green groups want the EPA to set. Brad Pinchuk, chief executive of Hirschbach Motor Lines, a midsize trucking firm, says some of his best drivers can get more than 10 miles per gallon out of their newest trucks today.  In East Dubuque, Pinchuk is buying new trucks from Navistar International Corp that use automatic transmissions to boost mileage. Looking at the monthly fuel usage of a driver who recently switched to an automatic transmission truck, Pinchuk says the new model shows a mile-per-gallon improvement.  Hirschbach also uses aerodynamic "sleds" and "tails" from startup SmartTruck, which attach to truck trailers and cut fuel usage by 10 percent by streamlining the flow of air around the trucks. Wabash National Corp offers a "skirts" and "tails" combination that provides similar savings. Wheel coverings from FlowBelow are another recent innovation, cutting fuel use by 3 percent, also by cutting the drag of air on the truck. Eaton Corp PLC is about to launch production of a dual-clutch transmission that it says will cut fuel consumption versus existing automatics by up to 12 percent. Engine maker Cummins Inc has a model in the pipeline that includes predictive GPS - which works out how to manage hills and valleys to use the least fuel. Klaus Kleinfeld, CEO of metals company Alcoa Inc, sees opportunities in the sector through increased use of aluminum to make trucks lighter. Daimler AG - the largest U.S. truck maker with 40 percent of the market so far this year last month showed off a Freightliner “SuperTruck” at an event in Las Vegas that has hit 12.2 miles per gallon in tests.  Its latest production model gets close to 9 miles per gallon. Daimler is pushing fuel saving technology into current trucks. So far this year, 66 percent of its Class 8 trucks are equipped with some form of automated transmission, up from 33 percent in 2013. But company executives caution some SuperTruck innovations may not be marketable in 10 years' time. The EPA should consider different ways trucks are driven and set flexible standards, Wolfgang Bernhard, head of Daimler’s global truck business, said in an interview.  "There's all different kinds of traffic," Bernhard said. "So you need to say what you mean by 10 miles per gallon." An EPA spokeswoman said the agency intends to propose "performance-based standards that provide for multiple technological pathways to compliance.” In other words, the agency wants to set a standard, and let truck makers and their customers decide what technology works best to hit the target. Kenny Vieth, president of ACT Research, which forecasts U.S. truck sales, says truck makers have reason to be wary of increasing costs. In 2005 and 2006, fleet owners splurged on new trucks to avoid buying 2007 models with expensive emission-reducing technology. "The whole industry has its fingers crossed that the EPA will focus on harvesting low-hanging fruit rather than home-run technologies that could prove expensive," Vieth said. At Hirschbach, Pinchuk has hired driver coaches to help improve driver efficiency. PeopleNet software in the trucks flags drivers for excessive repeated braking, which can indicate risky driving and also wastes fuel. Mesilla Valley Transportation CEO Royal Jones says many of his drivers average over 10 miles per gallon - though his fleet average is around 9 miles because short-haul drivers burn more fuel, since a truck can burn a gallon of diesel launching from a stop. MVT drivers have their top speed capped at 62 miles per hour using software, but any driver who gets over 8 miles per gallon is allowed to go up to 65 miles per hour. "If you're getting 10 miles per gallon, you're way ahead of the curve," Jones said. “But it is doable."