Scientists from Purdue University (United States) recently conducted a study comparing the performance of B20 (20% blend) soybean-based biodiesel and petroleum-based "Ultra Low Sulfur (ULS) Diesel" on a fleet of 20 trucks. The trucks were paired by make, model, mileage, and drive cycles, with ten trucks operated with the B20 biodiesel and ten trucks operated with ULS diesel. The performance indices for comparison (measured over a 12-month period) were: fuel consumption, idle time, truck speed, engine load, and engine speed. Fuel properties such as cetane number, energy content, density, kinematic viscosity, and lubricity were also measured for both fuels. Their results showed that "there [was] almost no statistical performance difference in semitrailer trucks using B20, a 20-percent blend of biodiesel, and No. 2 ultra-low sulfur diesel, the current standard". According to the Purdue University News article, "the only statistical difference related to the B20 was that it lowered the oil viscosity between maintenance intervals in engines slightly more than the ultra-low sulfur diesel". Nevertheless, the oil is said to still possess "sufficient viscosity so as not to damage engine parts". The study is published in the journal, Applied Engineering in Agriculture (URL above)..