GM exploring ways to raise half-ton Duramax diesel tow rating

Lots of truck owners cheered when GM announced fuel economy numbers for the 2020 Chevrolet Silverado with the 3.0-liter Duramax diesel inline-six. Even after Ram let loose its EPA mileage ratings for the 2020 Ram 1500 EcoDiesel, the Chevy oil-burner still took the trophy. The victory was years in the making, GM engineers spending an entire four-year development cycle refining the LM2 Duramax to increase mileage. The tradeoff, as well all know by now, is towing; the Duramax in half-ton duty pulls a maximum 9,300 pounds in the Silverado. Rivals across town can do more, the Ford F-150 PowerStroke rated at 11,500, the Ram 1500 EcoDiesel game to pull 12,560.

GM engineer John Barta told Muscle Cars & Trucks that more hauling chops could be on the way, explaining, “We’re actually looking at upgrading some of the materials around (the engine bay) to see if we can maybe raise our tow rating.”

Engine bay materials are at issue due to thermal complexities underhood. John Barta, GM’s assistant chief engineer of diesel engine controls, said the Duramax’s inline-six configuration allowed engineers to get emissions hardware like the combined selective catalytic reduction, diesel oxidation catalysts, and diesel particulate filter unit closer to the engine, where it heats up quicker, getting emissions down quicker. But that filter puts another heat source in those confines, enforcing a cap on the tow rating to keep the engine and other systems from overheating.

“If you look under the hood,” he said, “you’ll see a significant amount of silver ‘moon tape’ around to make sure things aren’t getting overheated… if we were to go up in higher towing, which we can, we start impacting the possibility of deteriorating some of the components.” There isn’t much space for more grille, so swapping for a better grade of “moon tape” or a different kind of material could reduce engine bay heat, extracting a higher tow rating in the process. 

It’s important to note a point Barta’s been making for months about the Duramax figures, though. “Even though it’s nice to brag about big numbers, in reality, light duty customers are not towing that large with their trucks,” and, “We do know that (95 percent) of our light duty customers don’t tow over 9,000 pounds.”

On our First Drive of the 2020 Silverado diesel we called out the tow rating, but emphasized that the Chevy and GMC have more important challenges to overcome. Our take was, “Even if we ultimately prefer the Duramax’s performance to the PowerStroke’s… it’s just not enough to counteract the Silverado’s uncompetitive interior and questionable ride quality.” Interior upgrades for the GM twins supposedly come our way for 2021, and it’s possible they’ll do more for sales than another 1,500 pounds hanging off the rear.