General Motors plans to offer full warranty coverage for fleets using approved B20 blended fuels in its 2011 model year heavy-duty pickups equipped with the Duramax 6.6L turbo diesel engine. The Durmax is covered under GM’s five-year/100,000 mile powertrain warranty.
Coleman Jones, GM’s biofuels implementation manager, said the automaker upgraded some seals and gasket materials in the Duramax’s fuel system to withstand the ester content of biodiesel – including an upgraded fuel filter that includes a coalescing element.
“This improves the separation of water that may be present in the fuel, because biodiesel can attract and absorb water,” he said. “Also, additional heating of the fuel circuit was added to reduce the chance of fuel gelling or waxing that could plug filters.”
B20 fuel is a blend of 20% biodiesel and 80% conventional diesel, and Jones noted GM has also added a new particulate regeneration system on the 2011 model Duramax that features a downstream injector; a feature that greatly reduces potential oil dilution, a concern when using biodiesel blended fuels. “Downstream injection saves fuel and works better with B20 than in-cylinder post injection,” he noted.
Jones added that the Duramx 6.6L underwent extensive testing and validation using B20 that met the ASTM International’s standard D7467, which covers biodiesel blends between B6 and B20. “True biodiesel is created through transesterfication and that’s what the Duramax 6.6L is designed to use,” he said.
The new Duramax will power the redesigned 2011 Chevy Silverado and GMC Sierra heavy-duty pickups, as well as the Chevrolet Express and GMC Savana full-size vans, GM noted.