Effects of intake air preheat were investigated on performance and emissions of a compression ignition engine running on fuel concentrations of biodiesel (85%)-methanol (15%), biodiesel (90%)-methanol (10%), biodiesel (95%)-methanol (5%), neat biodiesel (B100). Fuels were evaluated in the engine at two elevated intake air temperatures at 30 degrees C and 85 degrees C. Neat biodiesel and standard diesel fuels were used in the engine at the ambient air temperature. Performance and emissions of the diesel engine are compared based on biodiesel-methanol blends, neat biodiesel and standard diesel. The resulting emissions indicate that the high heat of vaporization of methanol affects CO and HC emissions significantly. Preheating the intake air or lowering the methanol concentration in biodiesel-methanol blends tends to reduce the production of CO and HC while increasing NO emission. (C) 2011 Elsevier Ltd. All rights reserved.