Push to zero emissions might be opening a door for propane engines

Nearly 500,000 United States Postal Service (USPS) employees are entrusted with delivering mail to every residential and business address in the U.S. each day. Much of that mail, though, first moves on contractor vehicles that transport it from distribution center to distribution center, and then to local post offices.

Some contractors are quite savvy, such as Butch McAbee and his wife, Lisa. The McAbees, who own McAbee Trucking in South Carolina, have held a USPS contract for 49 years and currently operate a fleet of 21 tractor-trailers and 15 straight trucks. For a mail operation, it is remarkably robust.

Lisa McAbee told FreightWaves the company likes to buy new equipment when possible, and a few years ago made the decision to move into alternative fuels. After a 2017 foray into compressed natural gas, the fleet is now adding propane vehicles.

“The United States Postal Service has its own sustainability plan,” McAbee said. “Since we’ve been in business with them for 49 years, we want to help them achieve that plan … by implementing propane rather than diesel into our contracts.”

McAbee Trucking will take delivery of a Ford F-650 with 26-foot van body with liftgate in April, and the plan is to acquire six additional vehicles — all Ford F-750 models with 26-foot van bodies. McAbee said the coronavirus has disrupted those plans, but they still expect to put them into operation this year. She said the vehicles are modified slightly to lessen the overall weight, allowing non-CDL drivers to drive them.

“It will still pull the same load and it will still get the same fuel mileage, and maybe even a little better fuel mileage because the truck is lighter,” she said.

Ford’s F-650 and F-750 models are also available with gas engines, but McAbee said that wasn’t a consideration for their trucks, which typically drive between 60,000 and 70,000 miles a year.

“We did not consider gas because propane emissions are less than gasoline and the cost for propane is still less than gas,” she said. “At one time [gas] would have been an option but now with the emissions it’s a no-brainer.”

The McAbees are exactly the type of customer who Tucker Perkins, president and CEO of the Propane Education & Research Council (PERC), thinks are perfect for propane. The trucks drive dedicated routes, can return to base for refueling, and are in line with industry pushes to reduce emissions. As Tucker sees it, that societal push toward zero emissions is opening the door for propane. A breakthrough in engine technology is only accelerating that push.

“For five years we’ve been working with Cummins on the next generation of propane engines,” Perkins said during the Green Truck Summit in Indianapolis earlier this month. “That’s the engine we’ve been waiting for to breach the Class 8 market.”

That engine, the Cummins 6.7L propane engine, leverages components from Cummins’ 6.7L diesel engine but is a direct propane injection powerplant that produces 880 lbs.-ft. of torque and 375 horsepower, Perkins said. Brake thermal efficiency (BTE) matches that of diesel and produces 11% less CO2 emissions than a diesel engine with a similar displacement.

Importantly, the engine produces between 17% and 25% less CO2 emissions than currently produced propane engines as a result of its BTE. Current propane engines include a Cummins 5.9L engine, a Ford 7.3L and a GM 6.6L.

The first part of the equation — the push to zero-emissions engines — is an inherent part of the propane story, Perkins noted. Propane engines, he said, can already meet the proposed NOx emissions standards. Current Environmental Protection Agency (EPA) standards call for engines to achieve 0.2 grams NOx per brake horsepower-hour (g/bhp-hr). In January, EPA issued an Advanced Notice of Proposed Rulemaking that would push that limit down to 0.02 g/bhp-hr. The rulemaking is in response to a push from California and 19 other states to lower the levels.

Perkins said propane engines already operate at 0.01 g/bhp-hr. Coming advances in direct injection, higher compression ratios, cooler exhaust gas recirculation, start/stop cylinder deactivation and hybrid solutions will help propane engines stay at these low levels.

The development of renewable propane that benefits from inexpensive and abundant feedstock ensures zero particulate matter release for the engines, another advantage over diesel, Perkins said.

The counterargument is that propane doesn’t have the same power as diesel, and with a lower British thermal unit (Btu) rating per gallon, fuel economy does suffer a little. However, the fuel is significantly cheaper than diesel and “its lower per-gallon cost can quickly offset the lower fuel economy,” the U.S. Department of Energy’s Alternative Fuels Data Center explained.

Steve Whaley, director of Autogas business development for PERC, told FreightWaves the average per-gallon price of propane, as of the beginning of March, was $1.27 on the West Coast and $1.45 on the East Coast. A 37-cents-per-gallon tax credit is also available currently, Whaley told FreightWaves at the Work Truck Show in Indianapolis.

“When you add up how much it costs to drive 100 miles, we’re 50% cheaper than diesel,” he said.

The other issue is infrastructure. Propane is not available at your regular fuel stop, and at this point, is best suited for operations where the vehicle returns to base or has propane fueling infrastructure along the way – exactly how McAbee Trucking plans to use its new propane trucks.

“It’s serving the same purpose as compressed natural gas but at a cheaper price,” Lisa McAbee said.

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Brian Straight

Brian Straight leads FreightWaves' Modern Shipper brand as Managing Editor. A journalism graduate of the University of Rhode Island, he has covered everything from a presidential election, to professional sports and Little League baseball, and for more than 10 years has covered trucking and logistics. Before joining FreightWaves, he was previously responsible for the editorial quality and production of Fleet Owner magazine and Brian lives in Connecticut with his wife and two kids and spends his time coaching his son’s baseball team, golfing with his daughter, and pursuing his never-ending quest to become a professional bowler. You can reach him at