The Effect of Biodiesel Fuels on the Low Temperature Operability of North American Heavy Duty Diesel Trucks 2008-01-2380

The use of renewable fuels, such as biodiesel, in motor vehicle fuels is expected to grow rapidly in North America as a result of government mandates, both federal and state/provincial. Biodiesel is a fuel component made from plant or animal feedstocks through a trans-esterification process. The resulting fatty acid methyl esters (FAME) have a large variation in cloud point from -5° C to +15° C, depending upon the source. In North America where a large geographic area experiences a cold climate, the poor low temperature properties of FAME and blends containing same (wax, gelling, and phase separation above the Cloud Point) could result in operability issues such as those experienced in Minnesota and Sweden.

To gain a better understanding of these concerns, a study was carried out to determine the low temperature operability limits of biodiesel fuels in 2003/2005 model year heavy-duty trucks in Imperial Oil's All-Weather Chassis Dynamometer (AWCD). Three Class 8 Heavy Duty trucks equipped with Detroit Diesel Series 60, Caterpillar C-12 and Cummins ISM engines were chosen and fitted appropriately to measure their performance under low temperature conditions. Three commercial ultra low sulfur diesel fuels having low cloud point were used as base fuel. Two base fuels and eight biodiesel fuels comprising B2 (2), B5 (5) and B20 (1) were made with canola methyl ester (CME), soybean methyl ester (SME), tallow methyl ester (TME) and palm methyl ester (PME). The properties were compared with the Canadian CGSB 3.520 specifications. All FAME's used met the ASTM D6751 specifications as well as the 200 seconds maximum cold soak filterability test with the exception of PME. The biodiesel fuel blends were tailored to meet the 2.5% Canadian low- end design temperature for January at two typical Canadian locations (-24°C and -37°C). The biodiesel fuels were then tested in the AWCD to determine the lowest operating temperature for each fuel in each truck. The low temperature operability was compared to laboratory tests: cloud point and Low Temperature Flow Test (LTFT) known as the best predictor of low temperature operability of North American diesel fuels for heavy duty diesel trucks. These results will provide guidance for blending biodiesel fuels to meet low temperature operability requirements in cold climates.