Three joint Government/Industry program have been reviewed to evaluate the effect of fuel properties and source on exhaust emissions from three post 1994 model year heavy-duty diesel engines, a single cylinder research engine and a prototype multicylinder engine designed to meet the 2004 model year oxides of nitrogen limit. The three post 1994 engines tested (at Environment Canada's facility) were a Detroit Diesel Series 50, a Caterpillar 3406E and a Cummins N14. Exhaust emissions of NOx, PM, CO, HC, and CO2 were measured using the “hot” US EPA Heavy-duty Transient Test Procedure. The single cylinder Ricardo Proteus research engine (run at the National Research Council of Canada) and the multicylinder Caterpillar 3176 prototype engine (run at the Southwest Research Institute) were tested using the AVL 8 mode test cycle.Fifteen fuels were tested in total: three “reference” Commercial Low Sulphur diesel fuels and twelve experimental fuels. The experimental fuels were blended from refinery streams in two sets of six fuels. One set of fuels was blended from oil sands derived components, the other from conventional crude derived components. The fuels were paired between the two sets: two pairs at approximately 10%, two pairs at 20% and two pairs at 30% total aromatic content by mass. Other fuel properties (including cetane number, sulphur and distillation) were controlled within a relatively narrow range for each pair of fuels. Due to testing constraints both the post 1994 and 2004 prototype multicylinder programs were tested on subsets of the experimental fuel matrix. The emission results are presented and discussed including a comparison between the different engine types.