The effects of fuel properties of both oil-sands-derived and conventional-crude-oil-derived diesel fuels were investigated on a single-cylinder DI research engine. The engine used in this study incorporated features of contemporary medium- to heavy-duty diesel engines and was tuned to the U.S. EPA 1994 emission standards. The engine experiments were run using the AVL 8-mode steady-state simulation of the U.S. EPA heavy-duty transient test procedure. The experimental fuels included 12 fuels blended using refinery streams to have controlled total aromatic levels and 7 other diesel fuels obtained from different sources. The results showed that at a constant cetane number (44) and sulfur content (150 ppm), oil-sands-derived fuels produced similar NOx emissions as their conventional-crude-oil-derived counterparts and total aromatic content and fuel density could be used in a regression model to predict NOx emissions. At the same total aromatic content, the oil sands derived fuel blends produced 5-10% higher PM emissions in the test engine, whereas at the same density, the two kinds of fuel blends produced similar PM emissions. Therefore, the higher PM emissions observed in oil-sands-derived fuel blends could be attributed to the higher densities of these fuels. Regression analysis showed that fuel density was a better descriptor for PM emissions than total aromatic content when the cetane number and sulfur content were kept constant.